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Monday, August 23, 2010

[T-SQL] Function to Retrieve First Word of Sentence

--This code/function can help to get you first word from a sentence.
--TEST SCRIPT
DECLARE @StringVar VARCHAR(100)
SET @StringVar = ' anything '
SELECT CASE CHARINDEX(' ', LTRIM(@StringVar), 1)
WHEN 0 THEN LTRIM(@StringVar)
ELSE SUBSTRING(LTRIM(@StringVar), 1, CHARINDEX(' ',LTRIM(@StringVar), 1) - 1)
END FirstWordofSentence

--FUNCTION CODE
CREATE FUNCTION GetFirstWord (@StringVar VARCHAR(MAX))
RETURNS VARCHAR(MAX)
AS
BEGIN
DECLARE @rtStringVar VARCHAR(MAX)
SELECT @rtStringVar = CASE CHARINDEX(' ', LTRIM(@StringVar), 1)
WHEN 0 THEN LTRIM(@StringVar)
ELSE SUBSTRING(LTRIM(@StringVar), 1, CHARINDEX(' ',LTRIM(@StringVar), 1) - 1)
END
RETURN @rtStringVar
END

Wednesday, August 18, 2010

[T-SQL] To concatenate the values of a column in all rows into one row.

USE pubs
GO
DECLARE @title_ids varchar(150), @delimiter char
SET @delimiter = ','
SELECT @title_ids = COALESCE(@title_ids + @delimiter, '') + title_id FROM titles
SELECT @title_ids AS [List of Title IDs]

[T-SQL] To convert a given string to proper case

CREATE FUNCTION PROPERCASE
(
--The string to be converted to proper case
@input varchar(8000)
)
--This function returns the proper case string of varchar type
RETURNS varchar(8000)
AS
BEGIN
IF @input IS NULL
BEGIN
--Just return NULL if input string is NULL
RETURN NULL
END

--Character variable declarations
DECLARE @output varchar(8000)
--Integer variable declarations
DECLARE @ctr int, @len int, @found_at int
--Constant declarations
DECLARE @LOWER_CASE_a int, @LOWER_CASE_z int, @Delimiter char(3), @UPPER_CASE_A int, @UPPER_CASE_Z int

--Variable/Constant initializations
SET @ctr = 1
SET @len = LEN(@input)
SET @output = ''
SET @LOWER_CASE_a = 97
SET @LOWER_CASE_z = 122
SET @Delimiter = ' ,-'
SET @UPPER_CASE_A = 65
SET @UPPER_CASE_Z = 90

WHILE @ctr <= @len BEGIN --This loop will take care of reccuring white spaces WHILE CHARINDEX(SUBSTRING(@input,@ctr,1), @Delimiter) > 0
BEGIN
SET @output = @output + SUBSTRING(@input,@ctr,1)
SET @ctr = @ctr + 1
END

IF ASCII(SUBSTRING(@input,@ctr,1)) BETWEEN @LOWER_CASE_a AND @LOWER_CASE_z
BEGIN
--Converting the first character to upper case
SET @output = @output + UPPER(SUBSTRING(@input,@ctr,1))
END
ELSE
BEGIN
SET @output = @output + SUBSTRING(@input,@ctr,1)
END

SET @ctr = @ctr + 1

WHILE CHARINDEX(SUBSTRING(@input,@ctr,1), @Delimiter) = 0 AND (@ctr <= @len)
BEGIN
IF ASCII(SUBSTRING(@input,@ctr,1)) BETWEEN @UPPER_CASE_A AND @UPPER_CASE_Z
BEGIN
SET @output = @output + LOWER(SUBSTRING(@input,@ctr,1))
END
ELSE
BEGIN
SET @output = @output + SUBSTRING(@input,@ctr,1)
END
SET @ctr = @ctr + 1
END

END
RETURN @output
END

[T-SQL] Get Biggest Table on Your Production DB

USE master
GO

IF EXISTS (SELECT 1 FROM sysobjects WHERE name = 'sp_show_huge_tables' AND type = 'P')
DROP PROC sp_show_huge_tables
GO

CREATE PROC sp_show_huge_tables
(
@top int = NULL,
@include_system_tables bit = 0
)
AS

BEGIN
IF @top > 0
SET ROWCOUNT @top

SELECT [Table Name], (SELECT rows FROM sysindexes s WHERE s.indid < 2 AND s.id = OBJECT_ID(a.[Table Name])) AS [Row count], [Total space used (MB)] FROM
(
SELECT QUOTENAME(USER_NAME(o.uid)) + '.' + QUOTENAME(OBJECT_NAME(i.id)) AS [Table Name],
CONVERT(numeric(15,2),(((CONVERT(numeric(15,2),SUM(i.reserved)) * (SELECT low FROM master.dbo.spt_values (NOLOCK) WHERE number = 1 AND type = 'E')) / 1024.)/1024.)) AS [Total space used (MB)]
FROM sysindexes i (NOLOCK)
INNER JOIN
sysobjects o (NOLOCK)
ON
i.id = o.id AND
((@include_system_tables = 1 AND o.type IN ('U', 'S')) OR o.type = 'U') AND
((@include_system_tables = 1)OR (OBJECTPROPERTY(i.id, 'IsMSShipped') = 0))
WHERE indid IN (0, 1, 255)
GROUP BY QUOTENAME(USER_NAME(o.uid)) + '.' + QUOTENAME(OBJECT_NAME(i.id))

) as a
ORDER BY [Total space used (MB)] DESC


SET ROWCOUNT 0
END

GO

GRANT EXEC ON sp_show_huge_tables TO Public

[T-SQL] Procedure to script your data (to generate INSERT statements from the existing data)

SET NOCOUNT ON
GO

PRINT 'Using Master database'
USE master
GO

PRINT 'Checking for the existence of this procedure'
IF (SELECT OBJECT_ID('sp_generate_inserts','P')) IS NOT NULL --means, the procedure already exists
BEGIN
PRINT 'Procedure already exists. So, dropping it'
DROP PROC sp_generate_inserts
END
GO

CREATE PROC sp_generate_inserts
(
@table_name varchar(776), -- The table/view for which the INSERT statements will be generated using the existing data
@target_table varchar(776) = NULL, -- Use this parameter to specify a different table name into which the data will be inserted
@include_column_list bit = 1, -- Use this parameter to include/ommit column list in the generated INSERT statement
@from varchar(800) = NULL, -- Use this parameter to filter the rows based on a filter condition (using WHERE)
@include_timestamp bit = 0, -- Specify 1 for this parameter, if you want to include the TIMESTAMP/ROWVERSION column's data in the INSERT statement
@debug_mode bit = 0, -- If @debug_mode is set to 1, the SQL statements constructed by this procedure will be printed for later examination
@owner varchar(64) = NULL, -- Use this parameter if you are not the owner of the table
@ommit_images bit = 0, -- Use this parameter to generate INSERT statements by omitting the 'image' columns
@ommit_identity bit = 0, -- Use this parameter to ommit the identity columns
@top int = NULL, -- Use this parameter to generate INSERT statements only for the TOP n rows
@cols_to_include varchar(8000) = NULL, -- List of columns to be included in the INSERT statement
@cols_to_exclude varchar(8000) = NULL, -- List of columns to be excluded from the INSERT statement
@disable_constraints bit = 0, -- When 1, disables foreign key constraints and enables them after the INSERT statements
@ommit_computed_cols bit = 0 -- When 1, computed columns will not be included in the INSERT statement

)
AS
BEGIN

/***********************************************************************************************************
Procedure: sp_generate_inserts (Build 22)
(Copyright © 2002 Narayana Vyas Kondreddi. All rights reserved.)

Purpose: To generate INSERT statements from existing data.
These INSERTS can be executed to regenerate the data at some other location.
This procedure is also useful to create a database setup, where in you can
script your data along with your table definitions.

Written by: Narayana Vyas Kondreddi
http://vyaskn.tripod.com

Acknowledgements:
Divya Kalra -- For beta testing
Mark Charsley -- For reporting a problem with scripting uniqueidentifier columns with NULL values
Artur Zeygman -- For helping me simplify a bit of code for handling non-dbo owned tables
Joris Laperre -- For reporting a regression bug in handling text/ntext columns

Tested on: SQL Server 7.0 and SQL Server 2000 and SQL Server 2005

Date created: January 17th 2001 21:52 GMT

Date modified: May 1st 2002 19:50 GMT

Email: vyaskn@hotmail.com

NOTE: This procedure may not work with tables with too many columns.
Results can be unpredictable with huge text columns or SQL Server 2000's sql_variant data types
Whenever possible, Use @include_column_list parameter to ommit column list in the INSERT statement, for better results
IMPORTANT: This procedure is not tested with internation data (Extended characters or Unicode). If needed
you might want to convert the datatypes of character variables in this procedure to their respective unicode counterparts
like nchar and nvarchar

ALSO NOTE THAT THIS PROCEDURE IS NOT UPDATED TO WORK WITH NEW DATA TYPES INTRODUCED IN SQL SERVER 2005 / YUKON


Example 1: To generate INSERT statements for table 'titles':

EXEC sp_generate_inserts 'titles'

Example 2: To ommit the column list in the INSERT statement: (Column list is included by default)
IMPORTANT: If you have too many columns, you are advised to ommit column list, as shown below,
to avoid erroneous results

EXEC sp_generate_inserts 'titles', @include_column_list = 0

Example 3: To generate INSERT statements for 'titlesCopy' table from 'titles' table:

EXEC sp_generate_inserts 'titles', 'titlesCopy'

Example 4: To generate INSERT statements for 'titles' table for only those titles
which contain the word 'Computer' in them:
NOTE: Do not complicate the FROM or WHERE clause here. It's assumed that you are good with T-SQL if you are using this parameter

EXEC sp_generate_inserts 'titles', @from = "from titles where title like '%Computer%'"

Example 5: To specify that you want to include TIMESTAMP column's data as well in the INSERT statement:
(By default TIMESTAMP column's data is not scripted)

EXEC sp_generate_inserts 'titles', @include_timestamp = 1

Example 6: To print the debug information:

EXEC sp_generate_inserts 'titles', @debug_mode = 1

Example 7: If you are not the owner of the table, use @owner parameter to specify the owner name
To use this option, you must have SELECT permissions on that table

EXEC sp_generate_inserts Nickstable, @owner = 'Nick'

Example 8: To generate INSERT statements for the rest of the columns excluding images
When using this otion, DO NOT set @include_column_list parameter to 0.

EXEC sp_generate_inserts imgtable, @ommit_images = 1

Example 9: To generate INSERT statements excluding (ommiting) IDENTITY columns:
(By default IDENTITY columns are included in the INSERT statement)

EXEC sp_generate_inserts mytable, @ommit_identity = 1

Example 10: To generate INSERT statements for the TOP 10 rows in the table:

EXEC sp_generate_inserts mytable, @top = 10

Example 11: To generate INSERT statements with only those columns you want:

EXEC sp_generate_inserts titles, @cols_to_include = "'title','title_id','au_id'"

Example 12: To generate INSERT statements by omitting certain columns:

EXEC sp_generate_inserts titles, @cols_to_exclude = "'title','title_id','au_id'"

Example 13: To avoid checking the foreign key constraints while loading data with INSERT statements:

EXEC sp_generate_inserts titles, @disable_constraints = 1

Example 14: To exclude computed columns from the INSERT statement:
EXEC sp_generate_inserts MyTable, @ommit_computed_cols = 1
***********************************************************************************************************/

SET NOCOUNT ON

--Making sure user only uses either @cols_to_include or @cols_to_exclude
IF ((@cols_to_include IS NOT NULL) AND (@cols_to_exclude IS NOT NULL))
BEGIN
RAISERROR('Use either @cols_to_include or @cols_to_exclude. Do not use both the parameters at once',16,1)
RETURN -1 --Failure. Reason: Both @cols_to_include and @cols_to_exclude parameters are specified
END

--Making sure the @cols_to_include and @cols_to_exclude parameters are receiving values in proper format
IF ((@cols_to_include IS NOT NULL) AND (PATINDEX('''%''',@cols_to_include) = 0))
BEGIN
RAISERROR('Invalid use of @cols_to_include property',16,1)
PRINT 'Specify column names surrounded by single quotes and separated by commas'
PRINT 'Eg: EXEC sp_generate_inserts titles, @cols_to_include = "''title_id'',''title''"'
RETURN -1 --Failure. Reason: Invalid use of @cols_to_include property
END

IF ((@cols_to_exclude IS NOT NULL) AND (PATINDEX('''%''',@cols_to_exclude) = 0))
BEGIN
RAISERROR('Invalid use of @cols_to_exclude property',16,1)
PRINT 'Specify column names surrounded by single quotes and separated by commas'
PRINT 'Eg: EXEC sp_generate_inserts titles, @cols_to_exclude = "''title_id'',''title''"'
RETURN -1 --Failure. Reason: Invalid use of @cols_to_exclude property
END


--Checking to see if the database name is specified along wih the table name
--Your database context should be local to the table for which you want to generate INSERT statements
--specifying the database name is not allowed
IF (PARSENAME(@table_name,3)) IS NOT NULL
BEGIN
RAISERROR('Do not specify the database name. Be in the required database and just specify the table name.',16,1)
RETURN -1 --Failure. Reason: Database name is specified along with the table name, which is not allowed
END

--Checking for the existence of 'user table' or 'view'
--This procedure is not written to work on system tables
--To script the data in system tables, just create a view on the system tables and script the view instead

IF @owner IS NULL
BEGIN
IF ((OBJECT_ID(@table_name,'U') IS NULL) AND (OBJECT_ID(@table_name,'V') IS NULL))
BEGIN
RAISERROR('User table or view not found.',16,1)
PRINT 'You may see this error, if you are not the owner of this table or view. In that case use @owner parameter to specify the owner name.'
PRINT 'Make sure you have SELECT permission on that table or view.'
RETURN -1 --Failure. Reason: There is no user table or view with this name
END
END
ELSE
BEGIN
IF NOT EXISTS (SELECT 1 FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME = @table_name AND (TABLE_TYPE = 'BASE TABLE' OR TABLE_TYPE = 'VIEW') AND TABLE_SCHEMA = @owner)
BEGIN
RAISERROR('User table or view not found.',16,1)
PRINT 'You may see this error, if you are not the owner of this table. In that case use @owner parameter to specify the owner name.'
PRINT 'Make sure you have SELECT permission on that table or view.'
RETURN -1 --Failure. Reason: There is no user table or view with this name
END
END

--Variable declarations
DECLARE @Column_ID int,
@Column_List varchar(8000),
@Column_Name varchar(128),
@Start_Insert varchar(786),
@Data_Type varchar(128),
@Actual_Values varchar(8000), --This is the string that will be finally executed to generate INSERT statements
@IDN varchar(128) --Will contain the IDENTITY column's name in the table

--Variable Initialization
SET @IDN = ''
SET @Column_ID = 0
SET @Column_Name = ''
SET @Column_List = ''
SET @Actual_Values = ''

IF @owner IS NULL
BEGIN
SET @Start_Insert = 'INSERT INTO ' + '[' + RTRIM(COALESCE(@target_table,@table_name)) + ']'
END
ELSE
BEGIN
SET @Start_Insert = 'INSERT ' + '[' + LTRIM(RTRIM(@owner)) + '].' + '[' + RTRIM(COALESCE(@target_table,@table_name)) + ']'
END


--To get the first column's ID

SELECT @Column_ID = MIN(ORDINAL_POSITION)
FROM INFORMATION_SCHEMA.COLUMNS (NOLOCK)
WHERE TABLE_NAME = @table_name AND
(@owner IS NULL OR TABLE_SCHEMA = @owner)



--Loop through all the columns of the table, to get the column names and their data types
WHILE @Column_ID IS NOT NULL
BEGIN
SELECT @Column_Name = QUOTENAME(COLUMN_NAME),
@Data_Type = DATA_TYPE
FROM INFORMATION_SCHEMA.COLUMNS (NOLOCK)
WHERE ORDINAL_POSITION = @Column_ID AND
TABLE_NAME = @table_name AND
(@owner IS NULL OR TABLE_SCHEMA = @owner)



IF @cols_to_include IS NOT NULL --Selecting only user specified columns
BEGIN
IF CHARINDEX( '''' + SUBSTRING(@Column_Name,2,LEN(@Column_Name)-2) + '''',@cols_to_include) = 0
BEGIN
GOTO SKIP_LOOP
END
END

IF @cols_to_exclude IS NOT NULL --Selecting only user specified columns
BEGIN
IF CHARINDEX( '''' + SUBSTRING(@Column_Name,2,LEN(@Column_Name)-2) + '''',@cols_to_exclude) <> 0
BEGIN
GOTO SKIP_LOOP
END
END

--Making sure to output SET IDENTITY_INSERT ON/OFF in case the table has an IDENTITY column
IF (SELECT COLUMNPROPERTY( OBJECT_ID(QUOTENAME(COALESCE(@owner,USER_NAME())) + '.' + @table_name),SUBSTRING(@Column_Name,2,LEN(@Column_Name) - 2),'IsIdentity')) = 1
BEGIN
IF @ommit_identity = 0 --Determing whether to include or exclude the IDENTITY column
SET @IDN = @Column_Name
ELSE
GOTO SKIP_LOOP
END

--Making sure whether to output computed columns or not
IF @ommit_computed_cols = 1
BEGIN
IF (SELECT COLUMNPROPERTY( OBJECT_ID(QUOTENAME(COALESCE(@owner,USER_NAME())) + '.' + @table_name),SUBSTRING(@Column_Name,2,LEN(@Column_Name) - 2),'IsComputed')) = 1
BEGIN
GOTO SKIP_LOOP
END
END

--Tables with columns of IMAGE data type are not supported for obvious reasons
IF(@Data_Type in ('image'))
BEGIN
IF (@ommit_images = 0)
BEGIN
RAISERROR('Tables with image columns are not supported.',16,1)
PRINT 'Use @ommit_images = 1 parameter to generate INSERTs for the rest of the columns.'
PRINT 'DO NOT ommit Column List in the INSERT statements. If you ommit column list using @include_column_list=0, the generated INSERTs will fail.'
RETURN -1 --Failure. Reason: There is a column with image data type
END
ELSE
BEGIN
GOTO SKIP_LOOP
END
END

--Determining the data type of the column and depending on the data type, the VALUES part of
--the INSERT statement is generated. Care is taken to handle columns with NULL values. Also
--making sure, not to lose any data from flot, real, money, smallmomey, datetime columns
SET @Actual_Values = @Actual_Values +
CASE
WHEN @Data_Type IN ('char','varchar','nchar','nvarchar')
THEN
'COALESCE('''''''' + REPLACE(RTRIM(' + @Column_Name + '),'''''''','''''''''''')+'''''''',''NULL'')'
WHEN @Data_Type IN ('datetime','smalldatetime')
THEN
'COALESCE('''''''' + RTRIM(CONVERT(char,' + @Column_Name + ',109))+'''''''',''NULL'')'
WHEN @Data_Type IN ('uniqueidentifier')
THEN
'COALESCE('''''''' + REPLACE(CONVERT(char(255),RTRIM(' + @Column_Name + ')),'''''''','''''''''''')+'''''''',''NULL'')'
WHEN @Data_Type IN ('text','ntext')
THEN
'COALESCE('''''''' + REPLACE(CONVERT(char(8000),' + @Column_Name + '),'''''''','''''''''''')+'''''''',''NULL'')'
WHEN @Data_Type IN ('binary','varbinary')
THEN
'COALESCE(RTRIM(CONVERT(char,' + 'CONVERT(int,' + @Column_Name + '))),''NULL'')'
WHEN @Data_Type IN ('timestamp','rowversion')
THEN
CASE
WHEN @include_timestamp = 0
THEN
'''DEFAULT'''
ELSE
'COALESCE(RTRIM(CONVERT(char,' + 'CONVERT(int,' + @Column_Name + '))),''NULL'')'
END
WHEN @Data_Type IN ('float','real','money','smallmoney')
THEN
'COALESCE(LTRIM(RTRIM(' + 'CONVERT(char, ' + @Column_Name + ',2)' + ')),''NULL'')'
ELSE
'COALESCE(LTRIM(RTRIM(' + 'CONVERT(char, ' + @Column_Name + ')' + ')),''NULL'')'
END + '+' + ''',''' + ' + '

--Generating the column list for the INSERT statement
SET @Column_List = @Column_List + @Column_Name + ','

SKIP_LOOP: --The label used in GOTO

SELECT @Column_ID = MIN(ORDINAL_POSITION)
FROM INFORMATION_SCHEMA.COLUMNS (NOLOCK)
WHERE TABLE_NAME = @table_name AND
ORDINAL_POSITION > @Column_ID AND
(@owner IS NULL OR TABLE_SCHEMA = @owner)


--Loop ends here!
END

--To get rid of the extra characters that got concatenated during the last run through the loop
SET @Column_List = LEFT(@Column_List,len(@Column_List) - 1)
SET @Actual_Values = LEFT(@Actual_Values,len(@Actual_Values) - 6)

IF LTRIM(@Column_List) = ''
BEGIN
RAISERROR('No columns to select. There should at least be one column to generate the output',16,1)
RETURN -1 --Failure. Reason: Looks like all the columns are ommitted using the @cols_to_exclude parameter
END

--Forming the final string that will be executed, to output the INSERT statements
IF (@include_column_list <> 0)
BEGIN
SET @Actual_Values =
'SELECT ' +
CASE WHEN @top IS NULL OR @top < 0 THEN '' ELSE ' TOP ' + LTRIM(STR(@top)) + ' ' END + '''' + RTRIM(@Start_Insert) + ' ''+' + '''(' + RTRIM(@Column_List) + '''+' + ''')''' + ' +''VALUES(''+ ' + @Actual_Values + '+'')''' + ' ' + COALESCE(@from,' FROM ' + CASE WHEN @owner IS NULL THEN '' ELSE '[' + LTRIM(RTRIM(@owner)) + '].' END + '[' + rtrim(@table_name) + ']' + '(NOLOCK)') END ELSE IF (@include_column_list = 0) BEGIN SET @Actual_Values = 'SELECT ' + CASE WHEN @top IS NULL OR @top < 0 THEN '' ELSE ' TOP ' + LTRIM(STR(@top)) + ' ' END + '''' + RTRIM(@Start_Insert) + ' '' +''VALUES(''+ ' + @Actual_Values + '+'')''' + ' ' + COALESCE(@from,' FROM ' + CASE WHEN @owner IS NULL THEN '' ELSE '[' + LTRIM(RTRIM(@owner)) + '].' END + '[' + rtrim(@table_name) + ']' + '(NOLOCK)') END --Determining whether to ouput any debug information IF @debug_mode =1 BEGIN PRINT '/*****START OF DEBUG INFORMATION*****' PRINT 'Beginning of the INSERT statement:' PRINT @Start_Insert PRINT '' PRINT 'The column list:' PRINT @Column_List PRINT '' PRINT 'The SELECT statement executed to generate the INSERTs' PRINT @Actual_Values PRINT '' PRINT '*****END OF DEBUG INFORMATION*****/' PRINT '' END PRINT '--INSERTs generated by ''sp_generate_inserts'' stored procedure written by Vyas' PRINT '--Build number: 22' PRINT '--Problems/Suggestions? Contact Vyas @ vyaskn@hotmail.com' PRINT '--http://vyaskn.tripod.com' PRINT '' PRINT 'SET NOCOUNT ON' PRINT '' --Determining whether to print IDENTITY_INSERT or not IF (@IDN <> '')
BEGIN
PRINT 'SET IDENTITY_INSERT ' + QUOTENAME(COALESCE(@owner,USER_NAME())) + '.' + QUOTENAME(@table_name) + ' ON'
PRINT 'GO'
PRINT ''
END


IF @disable_constraints = 1 AND (OBJECT_ID(QUOTENAME(COALESCE(@owner,USER_NAME())) + '.' + @table_name, 'U') IS NOT NULL)
BEGIN
IF @owner IS NULL
BEGIN
SELECT 'ALTER TABLE ' + QUOTENAME(COALESCE(@target_table, @table_name)) + ' NOCHECK CONSTRAINT ALL' AS '--Code to disable constraints temporarily'
END
ELSE
BEGIN
SELECT 'ALTER TABLE ' + QUOTENAME(@owner) + '.' + QUOTENAME(COALESCE(@target_table, @table_name)) + ' NOCHECK CONSTRAINT ALL' AS '--Code to disable constraints temporarily'
END

PRINT 'GO'
END

PRINT ''
PRINT 'PRINT ''Inserting values into ' + '[' + RTRIM(COALESCE(@target_table,@table_name)) + ']' + ''''


--All the hard work pays off here!!! You'll get your INSERT statements, when the next line executes!
EXEC (@Actual_Values)

PRINT 'PRINT ''Done'''
PRINT ''


IF @disable_constraints = 1 AND (OBJECT_ID(QUOTENAME(COALESCE(@owner,USER_NAME())) + '.' + @table_name, 'U') IS NOT NULL)
BEGIN
IF @owner IS NULL
BEGIN
SELECT 'ALTER TABLE ' + QUOTENAME(COALESCE(@target_table, @table_name)) + ' CHECK CONSTRAINT ALL' AS '--Code to enable the previously disabled constraints'
END
ELSE
BEGIN
SELECT 'ALTER TABLE ' + QUOTENAME(@owner) + '.' + QUOTENAME(COALESCE(@target_table, @table_name)) + ' CHECK CONSTRAINT ALL' AS '--Code to enable the previously disabled constraints'
END

PRINT 'GO'
END

PRINT ''
IF (@IDN <> '')
BEGIN
PRINT 'SET IDENTITY_INSERT ' + QUOTENAME(COALESCE(@owner,USER_NAME())) + '.' + QUOTENAME(@table_name) + ' OFF'
PRINT 'GO'
END

PRINT 'SET NOCOUNT OFF'


SET NOCOUNT OFF
RETURN 0 --Success. We are done!
END

GO

PRINT 'Created the procedure'
GO


--Mark procedure as system object
EXEC sys.sp_MS_marksystemobject sp_generate_inserts
GO

PRINT 'Granting EXECUTE permission on sp_generate_inserts to all users'
GRANT EXEC ON sp_generate_inserts TO public

SET NOCOUNT OFF
GO

PRINT 'Done'

/*
Usage:

Example 1: To generate INSERT statements for table 'titles':
EXEC sp_generate_inserts 'titles'
Example 2: To ommit the column list in the INSERT statement: (Column list is included by default)
NOTE: If you have too many columns, you are advised to ommit column list, as shown below, to avoid erroneous results
EXEC sp_generate_inserts 'titles', @Include_Column_List = 0
Example 3: To generate INSERT statements for 'titlesCopy' table from 'titles' table:
EXEC sp_generate_inserts 'titles', 'titlesCopy'
Example 4: To generate INSERT statements for 'titles' table for only those titles which contain the word 'Computer' in them:
EXEC sp_generate_inserts 'titles', @From = "from titles where title like '%Computer%'"
Example 5: To specify that you want to include TIMESTAMP column's data as well in the INSERT statement:
NOTE: By default TIMESTAMP column's data is not scripted
EXEC sp_generate_inserts 'titles', @Include_Timestamp = 1
Example 6: To print the debug information:
EXEC sp_generate_inserts 'titles', @debug_mode = 1
Example 7: If you are not the owner of the table, use @owner parameter to specify the owner name:
NOTE: To use this option, you must have SELECT permissions on that table
EXEC sp_generate_inserts Nickstable, @owner = 'Nick'
Example 8: To generate INSERT statements for the rest of the columns excluding images:
NOTE: When using this otion, DO NOT set @include_column_list parameter to 0
EXEC sp_generate_inserts imgtable, @ommit_images = 1
Example 9: To generate INSERT statements for the rest of the columns excluding IDENTITY column:
EXEC sp_generate_inserts mytable, @ommit_identity = 1
Example 10: To generate INSERT statements for the top 10 rows in the table:
EXEC sp_generate_inserts mytable, @top = 10
Example 11: To generate INSERT statements only with the columns you want:
EXEC sp_generate_inserts titles, @cols_to_include = "'title','title_id','au_id'"
Example 12: To generate INSERT statements by ommitting some columns:
EXEC sp_generate_inserts titles, @cols_to_exclude = "'title','title_id','au_id'"
Example 13: To avoid checking the foreign key constraints while loading data with INSERT statements:
NOTE: The @disable_constraints option will disable foreign key constraints, by assuming that the source data is valid and referentially sound
EXEC sp_generate_inserts titles, @disable_constraints = 1
Example 14: To avoid scripting data from computed columns:
EXEC sp_generate_inserts MyTable, @ommit_computed_cols = 1

*/

[T-SQL] Script for Split Function

CREATE FUNCTION dbo.Split(@String varchar(8000), @Delimiter char(1))
returns @temptable TABLE (items varchar(8000))
as
begin
declare @idx int
declare @slice varchar(8000)

select @idx = 1
if len(@String)<1 or @String is null return while @idx!= 0 begin set @idx = charindex(@Delimiter,@String) if @idx!=0 set @slice = left(@String,@idx - 1) else set @slice = @String if(len(@slice)>0)
insert into @temptable(Items) values(@slice)

set @String = right(@String,len(@String) - @idx)
if len(@String) = 0 break
end
return
end
--how to use
select top 10 * from dbo.split('Karachi , Lahore , Isb',',')

Monday, August 16, 2010

[T-SQL] Shrink log in all your user databases

DECLARE @SQL NVARCHAR(MAX)

SELECT @SQL = COALESCE(@SQL + CHAR(13) + CHAR(10),'') + N'
Use ' + QUOTENAME(d.[name]) + ';' + CHAR(13) + '
ALTER DATABASE ' + QUOTENAME(d.[name]) + ' SET RECOVERY SIMPLE;
DBCC SHRINKFILE (' + QUOTENAME(mf.[name],'''') + ', 1);
ALTER DATABASE ' + QUOTENAME(d.[name]) + ' SET RECOVERY FULL;'
FROM sys.databases d
INNER JOIN sys.master_files mf ON [d].[database_id] = [mf].[database_id]
WHERE
d.[database_id] > 4 --no sys dbs
AND d.recovery_model = 1
AND d.is_read_only = 0
AND mf.[type] = 1 --log files
ORDER BY d.name

--print @SQL

EXECUTE (@SQL)

[T-SQL] How to search for all words inclusive without using Full Text search

DECLARE @MyTable TABLE (Id INT IDENTITY(1,1), Searched VARCHAR(200))
DECLARE @Keys TABLE (Word VARCHAR(200), WordId INT IDENTITY(1,1))

INSERT INTO @MyTable VALUES ('Mother Father Daughter Son')
INSERT INTO @MyTable VALUES ('Mother Daughter Son')
INSERT INTO @MyTable VALUES ('Mother Son')
INSERT INTO @MyTable VALUES ('Daughter Son')
INSERT INTO @MyTable VALUES ('Mother Father Son')
INSERT INTO @MyTable VALUES ('Son Daughter Father')
INSERT INTO @MyTable VALUES ('Mother Son')
INSERT INTO @MyTable VALUES ('Other Word')
INSERT INTO @MyTable VALUES ('Mother Father Daughter Brother Son')
INSERT INTO @MyTable VALUES ('Mother Daughter Son Stepdaughter')
INSERT INTO @MyTable VALUES ('Mother Son And Stepson and Daughter and Father and Grandfather')
INSERT INTO @MyTable VALUES ('Daughter Son Family')
INSERT INTO @MyTable VALUES ('Mother Brother Father Son Orphan')
INSERT INTO @MyTable VALUES ('Son or Daughter or Father')
INSERT INTO @MyTable VALUES ('Mother And Son')
INSERT INTO @MyTable VALUES ('Other Word One More')

INSERT INTO @Keys VALUES ('Mother')
INSERT INTO @Keys VALUES ('Father')
INSERT INTO @Keys VALUES ('Son')
INSERT INTO @Keys VALUES ('Daughter')

DECLARE @nAllWords INT
SELECT @nAllWords = COUNT(*) FROM @Keys

SELECT MyTable.*
FROM @MyTable MyTable
INNER JOIN (SELECT MyTable.Id
FROM @MyTable MyTable
INNER JOIN @Keys KeyWords ON ' ' + MyTable.Searched + ' ' LIKE '% ' + KeyWords.Word + ' %'
GROUP BY MyTable.Id
HAVING COUNT(DISTINCT(KeyWords.Word)) = @nAllWords) Tbl1 ON MyTable.Id = Tbl1.Id

Wednesday, August 11, 2010

[T-SQL] How to see sql server configurations

SELECT *
FROM sys.configurations

[T-SQL] Introduction to BINARY_CHECKSUM and Working Example

Following example is modified from the original example taken from BOL.

USE AdventureWorks;
GO
-- Create table
IF EXISTS (SELECT * FROM sys.objects WHERE OBJECT_ID = OBJECT_ID(N'[dbo].[myTable]') AND TYPE IN (N'U'))
DROP TABLE [dbo].[myTable]
GO
CREATE TABLE myTable (column1 INT, column2 VARCHAR(256));
GO
-- Insert Value
INSERT INTO myTable VALUES (1, 'test');
GO
-- Check the Checksum
SELECT BINARY_CHECKSUM(*) AS BCH FROM myTable;
GO
-- Change the value
UPDATE myTable SET column2 = 'TEST';
GO
-- Check the Checksum
SELECT BINARY_CHECKSUM(*) AS BCH FROM myTable;
GO
-- Change the value
UPDATE myTable SET column2 = 'test';
GO
-- Check the Checksum
SELECT BINARY_CHECKSUM(*) AS BCH FROM myTable;
GO
-- Clean up
DROP TABLE [dbo].[myTable]
GO

Thursday, August 5, 2010

[T-SQL] Difference Between GRANT and WITH GRANT

Let us first see the syntax and analyze.

GRANT:
USE master;
GRANT VIEW ANY DATABASE TO username;
GO

WITH GRANT:
USE master;
GRANT VIEW ANY DATABASE TO username WITH GRANT OPTION;
GO


The difference between these options is very simple. In case of only GRANT, the username cannot grant the same permission to other users. On the other hand, with the option WITH GRANT, the username will be able to give the permission after receiving requests from other users.

[T-SQL] Script to Take Database Offline – Take Database Online

-- Create Test DB
CREATE DATABASE [myDB]
GO
-- Take the Database Offline
ALTER DATABASE [myDB] SET OFFLINE WITH
ROLLBACK IMMEDIATE
GO
-- Take the Database Online
ALTER DATABASE [myDB] SET ONLINE
GO
-- Clean up
DROP DATABASE [myDB]
GO

[T-SQL] Attach mdf file without ldf file in Database

USE [master]
GO
-- Method 1: I use this method
EXEC sp_attach_single_file_db @dbname='TestDb',
@physname=N'C:\Program Files\Microsoft SQL Server\MSSQL10.MSSQLSERVER\MSSQL\DATA\TestDb.mdf'
GO
-- Method 2:
CREATE DATABASE TestDb ON
(FILENAME = N'C:\Program Files\Microsoft SQL Server\MSSQL10.MSSQLSERVER\MSSQL\DATA\TestDb.mdf')
FOR ATTACH_REBUILD_LOG
GO

[T-SQL] GUID vs INT

INT
Advantage:

1.Numeric values (and specifically integers) are better for performance when used in joins, indexes and conditions.
2.Numeric values are easier to understand for application users if they are displayed.
Disadvantage:

1.If your table is large, it is quite possible it will run out of it and after some numeric value there will be no additional identity to use.
GUID
Advantage:

1.Unique across the server.
Disadvantage:

1.String values are not as optimal as integer values for performance when used in joins, indexes and conditions.
2.More storage space is required than INT

[T-SQL] Disable Clustered Index and Data Insert

Let us go over this example where inserting the data is not possible when a clustered index is disabled.

USE AdventureWorks
GO
-- Create Table
CREATE TABLE [dbo].[TableName](
[ID] [int] NOT NULL,
[FirstCol] [varchar](50) NULL,
CONSTRAINT [PK_TableName] PRIMARY KEY CLUSTERED
([ID] ASC)
)
GO
-- Create Nonclustered Index
CREATE UNIQUE NONCLUSTERED INDEX [IX_NonClustered_TableName] ON [dbo].[TableName]
([FirstCol] ASC)
GO
-- Populate Table
INSERT INTO [dbo].[TableName]
SELECT 1, 'First'
UNION ALL
SELECT 2, 'Second'
UNION ALL
SELECT 3, 'Third'
GO
-- Disable Nonclustered Index
ALTER INDEX [IX_NonClustered_TableName] ON [dbo].[TableName] DISABLE
GO
-- Insert Data should work fine
INSERT INTO [dbo].[TableName]
SELECT 4, 'Fourth'
UNION ALL
SELECT 5, 'Fifth'
GO
-- Disable Clustered Index
ALTER INDEX [PK_TableName] ON [dbo].[TableName] DISABLE
GO
-- Insert Data will fail
INSERT INTO [dbo].[TableName]
SELECT 6, 'Sixth'
UNION ALL
SELECT 7, 'Seventh'
GO
/*
Error: Msg 8655, Level 16, State 1, Line 1
The query processor is unable to produce a plan because the index 'PK_TableName' on table or view 'TableName' is disabled.
*/
-- Reorganizing Index will also throw an error
ALTER INDEX [PK_TableName] ON [dbo].[TableName] REORGANIZE
GO
/*
Error: Msg 1973, Level 16, State 1, Line 1
Cannot perform the specified operation on disabled index 'PK_TableName' on table 'dbo.TableName'.
*/
-- Rebuliding should work fine
ALTER INDEX [PK_TableName] ON [dbo].[TableName] REBUILD
GO
-- Insert Data should work fine
INSERT INTO [dbo].[TableName]
SELECT 6, 'Sixth'
UNION ALL
SELECT 7, 'Seventh'
GO
-- Clean Up
DROP TABLE [dbo].[TableName]
GO

[T-SQL] DATE and TIME in SQL Server 2008

Example of Date and Time

DECLARE @varDate AS DATE
DECLARE @varTime AS TIME
SET @varDate = '10/10/2010'
SET @varTime = '12:12:12'
SELECT CAST(@varDate AS DATETIME) C_Date
SELECT CAST(@varTime AS DATETIME) C_Time

Result would be

2010-10-10 00:00:00
1900-01-01 12:12:12

[T-SQL] Merge Operator

Let us run the same example which I have used earlier; I am listing the same here again for convenience.

--Let’s create Student Details and StudentTotalMarks and inserted some records.
USE tempdb
GO
CREATE TABLE StudentDetails
(
StudentID INTEGER PRIMARY KEY,
StudentName VARCHAR(15)
)
GO
INSERT INTO StudentDetails
VALUES(1,'SMITH')
INSERT INTO StudentDetails
VALUES(2,'ALLEN')
INSERT INTO StudentDetails
VALUES(3,'JONES')
INSERT INTO StudentDetails
VALUES(4,'MARTIN')
INSERT INTO StudentDetails
VALUES(5,'JAMES')
GO
CREATE TABLE StudentTotalMarks
(
StudentID INTEGER REFERENCES StudentDetails,
StudentMarks INTEGER
)
GO
INSERT INTO StudentTotalMarks
VALUES(1,230)
INSERT INTO StudentTotalMarks
VALUES(2,255)
INSERT INTO StudentTotalMarks
VALUES(3,200)
GO
-- Select from Table
SELECT *
FROM StudentDetails
GO
SELECT *
FROM StudentTotalMarks
GO
-- Merge Statement
MERGE StudentTotalMarks AS stm
USING (SELECT StudentID,StudentName FROM StudentDetails) AS sd
ON stm.StudentID = sd.StudentID
WHEN MATCHED AND stm.StudentMarks > 250 THEN DELETE
WHEN MATCHED THEN UPDATE SET stm.StudentMarks = stm.StudentMarks + 25
WHEN NOT MATCHED THEN
INSERT(StudentID,StudentMarks)
VALUES(sd.StudentID,25);
GO
-- Select from Table
SELECT *
FROM StudentDetails
GO
SELECT *
FROM StudentTotalMarks
GO
-- Clean up
DROP TABLE StudentDetails
GO
DROP TABLE StudentTotalMarks
GO

[T-SQL] Precision of SMALLDATETIME – A 1 Minute Precision

SQL SERVER – Precision of SMALLDATETIME – A 1 Minute Precision
June 1, 2010 by pinaldave

I am myself surprised that I am writing this post today. I am going to present one of the very known facts of SQL Server SMALLDATETIME datatype. Even though this is a very well-known datatype, many a time, I have seen developers getting confused with precision of the SMALLDATETIME datatype.

The precision of the datatype SMALLDATETIME is 1 minute. It discards the seconds by rounding up or rounding down any seconds greater than zero. Let us see the following example

DECLARE @varSDate AS SMALLDATETIME
SET @varSDate = '1900-01-01 12:12:01'
SELECT @varSDate C_SDT
SET @varSDate = '1900-01-01 12:12:29'
SELECT @varSDate C_SDT
SET @varSDate = '1900-01-01 12:12:30'
SELECT @varSDate C_SDT
SET @varSDate = '1900-01-01 12:12:59'
SELECT @varSDate C_SDT

[T-SQL] Difference Between GETDATE and SYSDATETIME

Sometime something so simple skips our mind. I never knew the difference between GETDATE and SYSDATETIME. I just ran simple query as following and realized the difference.

SELECT GETDATE() fn_GetDate, SYSDATETIME() fn_SysDateTime

In case of GETDATE the precision is till miliseconds and in case of SYSDATETIME the precision is till nanoseconds.

[T-SQL] Self Join – Inner Join and Outer Join

USE TempDb
GO
-- Create a Table
CREATE TABLE Employee(
EmployeeID INT PRIMARY KEY,
Name NVARCHAR(50),
ManagerID INT
)
GO
-- Insert Sample Data
INSERT INTO Employee
SELECT 1, 'Mike', 3
UNION ALL
SELECT 2, 'David', 3
UNION ALL
SELECT 3, 'Roger', NULL
UNION ALL
SELECT 4, 'Marry',2
UNION ALL
SELECT 5, 'Joseph',2
UNION ALL
SELECT 7, 'Ben',2
GO
-- Check the data
SELECT *
FROM Employee
GO



We will now use inner join to find the employees and their managers’ details.

-- Inner Join
SELECT e1.Name EmployeeName, e2.name AS ManagerName
FROM Employee e1
INNER JOIN Employee e2
ON e1.ManagerID = e2.EmployeeID
GO



From the result set, we can see that all the employees who have a manager are visible. However we are unable to find out the top manager of the company as he is not visible in our resultset. The reason for the same is that due to inner join, his name is filtered out. Inner join does not bring any result which does not have manager id. Let us convert Inner Join to Outer Join and then see the resultset.

-- Outer Join
SELECT e1.Name EmployeeName, ISNULL(e2.name, 'Top Manager') AS ManagerName
FROM Employee e1
LEFT JOIN Employee e2
ON e1.ManagerID = e2.EmployeeID
GO



Once we convert Inner Join to Outer Join, we can see the Top Manager as well. Here we have seen how Self Join can behave as an inner join as well as an outer join.

[T-SQL] Datetime Function SWITCHOFFSET Example

I was recently asked if I know how SWITCHOFFSET works. This feature only works in SQL Server 2008.

Here is quick definition of the same from BOL: Returns a datetimeoffset value that is changed from the stored time zone offset to a specified new time zone offset.

What essentially it does is that changes the current offset of the time to any other offset which we defined. Let us see the example of the same.

SELECT SYSDATETIMEOFFSET() GetCurrentOffSet;
SELECT SWITCHOFFSET(SYSDATETIMEOFFSET(), '-04:00') 'GetCurrentOffSet-4';
SELECT SWITCHOFFSET(SYSDATETIMEOFFSET(), '-02:00') 'GetCurrentOffSet-2';
SELECT SWITCHOFFSET(SYSDATETIMEOFFSET(), '+00:00') 'GetCurrentOffSet+0';
SELECT SWITCHOFFSET(SYSDATETIMEOFFSET(), '+02:00') 'GetCurrentOffSet+2';
SELECT SWITCHOFFSET(SYSDATETIMEOFFSET(), '+04:00') 'GetCurrentOffSet+4';

The example above clearly shows that Switch offset does not only change the offset; it also alters the current time. If you look at GetcurrentOffset, it is +5.30; but, you will notice that GetCurrentOffset-2 does not only change the offset to -2. It also changes the time with the appropriate time at Timezone -2.

I suggest that you run the code in SSMS Query Window and observe the code behavior.

[T-SQL] Dual - Oracle

What is the Equivalent of DUAL in SQL Server to get current datetime?
Oracle:

select sysdate from dual

SQL Server:

SELECT GETDATE()

What is the equivalent of DUAL in SQL Server?
None. There is no need of Dual table in SQL Server at all.

Oracle:

select ‘something’ from dual

SQL Server:

SELECT ‘something’

I have to have DUAL table in SQL Server, what is the workaround?
If you have transferred your code from Oracle and you do not want to remove DUAL yet, you can create a DUAL table yourself in the SQL Server and use it.

Here is a quick script to do the said procedure.

CREATE TABLE DUAL
(
DUMMY VARCHAR(1)
)
GO
INSERT INTO DUAL (DUMMY)
VALUES ('X')
GO

After creating the DUAL table above just like in Oracle, you can now use DUAL table in SQL Server.

[T-SQL] ERROR: 8170 Insufficient result space to convert uniqueidentifier value to char

I just came across very simple error and the solution was even simpler. While concatenating NEWID to another varchar string, I had to CONVERT/CAST it to VARCHAR and I accidentally put length of VARCHAR to 10 instead of 36. It displayed following error.

Msg 8170, Level 16, State 2, Line 1
Insufficient result space to convert uniqueidentifier value to char.

The code which I had ran earlier was as following.

SELECT 'GeneratedID:'+CAST(NEWID() AS VARCHAR(10)) AS NEW_ID


Solution:

The solution of above error is extremely simple. I just increased the length from VARCHAR(10) to VARCHAR(36) and it worked fine.

SELECT 'GeneratedID:'+CAST(NEWID() AS VARCHAR(36)) AS NEW_ID

[T-SQL] Computed Column – PERSISTED and Storage

Many people think that as soon as computed columns are created the column is materialized and the data is now stored in the column just like usual. In fact this is not true. If computed column is not marked as persisted, it is not created when the column is created, in fact it is still computed at run time. Once you mark column as persisted, it is computed right away and stored in the data table.

Let us see quickly following example of the creating computed column.

USE tempdb
GO
-- Create Table
CREATE TABLE UDFEffect (ID INT,
FirstName VARCHAR(100),
LastName VARCHAR(100))
GO
-- Insert One Hundred Thousand Records
INSERT INTO UDFEffect (ID,FirstName,LastName)
SELECT TOP 100000 ROW_NUMBER() OVER (ORDER BY a.name) RowID,
'Bob',
CASE WHEN ROW_NUMBER() OVER (ORDER BY a.name)%2 = 1 THEN 'Smith'
ELSE 'Brown' END
FROM sys.all_objects a
CROSS JOIN sys.all_objects b
GO
-- Check the space used by table
sp_spaceused 'UDFEffect'
GO
-- Add Computed Column
ALTER TABLE dbo.UDFEffect ADD
FullName AS (FirstName+' '+LastName)
GO
-- Check the space used by table
sp_spaceused 'UDFEffect'
GO
-- Add Computed Column PERSISTED
ALTER TABLE dbo.UDFEffect ADD
FullName_P AS (FirstName+' '+LastName) PERSISTED
GO
-- Check the space used by table
sp_spaceused 'UDFEffect'
GO
-- Clean up Database
DROP TABLE UDFEffect
GO

I have used the system stored procedure sp_spaceused to find out the space used in the query.

From the resultset it is very clear that when I created the computed column, it did not take any additional space in the database. However, when I created computed column marked as PERSISTED it indeed took more space in the data table and the size of the table is grown larger.



I hope this clear it up. In future article I will write performance and efficiency of the computed columns.

[T-SQL] Advanced Server Configuration

“How I check all the advanced configuration of the SQL Server?”

EXEC sp_configure 'Show Advanced Options', 1;
GO
RECONFIGURE;
GO
EXEC sp_configure;

[T-SQL] Identity Columns

Allowing inserts to identity columns:

If you are inserting data from some other source to a table with an identity column and you need to ensure you retain the indentity values, you can temporarily allow inserts to the indentity column. Without doing so explicitly you will receive an error if you attempt to insert a value into the indentity column. For example, if I have a table named MYTABLE and I want to allow inserts into it's identity column, I can execute the following:


set identity_insert mytable on

Once you execute the command you will be able to insert values into the table's identity column. This will stay in effect in until you turn it off by executing the following:


set identity_insert mytable off

Be aware that at any time, only a single table in a session can have the identity_insert set to on. If you attempt to enable this for a table and another table already has this enabled, you will receive an error and will not be able to do so until you first turn this off for the other table. Also, if the value used for the indentity is larger than the current identity value then the new value will be used for the identity seed for the column.



Reseeding the identity value:

You can reseed the indentity value, that is, to have the identity values reset or start at a new predefined value by using DBCC CHECKIDENT. For example, if I have a table named MYTABLE and I want to reseed the indentity column to 30 I would execute the following:


dbcc checkident (mytable, reseed, 30)

If you wanted to reseed the table to start with an identity of 1 with the next insert then you would reseed the table's identity to 0. The identity seed is what the value is currently at, meaning that the next value will increment the seed and use that. However, one thing to keep in mind is that if you set the identity seed below values that you currently have in the table, that you will violate the indentity column's uniqueness constraint as soon as the values start to overlap. The identity value will not just “skip” values that already exist in the table.