/*    Description: UTILITY - Locate in MASTER


        Syntax: EXEC sp_RemoveDups TableName, DupQualifierFieldNameList, DeleteDups, UniqueColName, CreateIdentColIfNeeded, StoredProcedureResult
           Only the first two arguments are required
           For HELP, enter the stored procedures name without any arguments or see the PRINT statements below
           NO DELETION WILL OCCUR by default - only duplicate recordset returned.  To delete records, pass in a 0 for the DeleteDups argument.

       Example: EXEC sp_RemoveDups 'MyTable','LastName,FirstName,HomePhone'

         Purpose: Allow removal of duplicate rows where
           1. We define what fields qualify the duplicate
           2. We select the unique rowid or it is detected automatically else no action takes place

   Method:        Delete by RowID all duplicate rows except the highest RowID (in alpha-sort sequence)
           of each group of duplicates.

        DATE        BY                CHANGE
   09-23-2002    Frank                Original v1.0
   09-23-2002    Frank                Changed the name from sp_RemoveDupsByRowID to sp_RemoveDups
   10-8-2002    Sean P. O. MacCath-Moran    Made @UniqueColName optional
   Added logic to auto-detect RowGUID and Identity columns
   Added logic to check for unique value column if no RowGUID or Identity column exists
   Added logic to create a temporary ID field as a last resort if no unique column could be located
   Added HELP

*/

CREATE PROCEDURE sp_RemoveDups
@TableName as varchar(50) = NULL,
@DupQualifierFieldNameList as varchar(200) = NULL,
@DeleteDups as bit = NULL,
@UniqueColName as varchar(50) = NULL,
@CreateIdentColIfNeeded as bit = NULL,
@StoredProcedureResult int = NULL OUTPUT

AS
SET NOCOUNT ON

DECLARE @SQL nvarchar(2000)
DECLARE @SQL_DetermineUniqueTemplate nvarchar(2000)
DECLARE @TempIdentColName varchar(20)
DECLARE @HostName varchar(50)
DECLARE @ActionText varchar(10)

DECLARE @SUM int
DECLARE @COUNT int
DECLARE @NextColumn varchar(50)


/*==================================================================================*/
/*========================VARIABLE INITIALIZATION AND SETUP========================*/
/*=================================================================================*/
/*If no unique column is located then a temporary Identity column will be created useing the name specified in this TempIdentColName string*/
SET @TempIdentColName = 'TempIdentityColXY123'

SET @SQL_DetermineUniqueTemplate = 'SELECT @COUNT = COUNT(Count), @SUM = sum(Count) from '
SET @SQL_DetermineUniqueTemplate = @SQL_DetermineUniqueTemplate + CHAR(13) + '(SELECT TOP 100 PERCENT , COUNT(*) as Count FROM ' + @TableName
SET @SQL_DetermineUniqueTemplate = @SQL_DetermineUniqueTemplate + CHAR(13) + ' GROUP BY  ORDER BY ) a'

/*Retrieve the Host Name.  This will be used later in this SP as a test to determine if the user is making this call from within SQL Query Analyzer*/
SELECT @HostName = hostname FROM master..sysprocesses WHERE spid = @@SPID AND program_name = 'SQL Query Analyzer'


/*Set ActionText to be used in message output*/
IF (@DeleteDups IS NULL) OR (@DeleteDups = 1)
   SET @ActionText = 'Selection'
ELSE
   SET @ActionText = 'Deletion'

/*If a value is specified for use by UniqueColName it cannot exist in the columns from the DupQualifierFieldNameList*/
IF CHARINDEX(@UniqueColName, @DupQualifierFieldNameList) > 0
   BEGIN
       /*The value in UniqueColName was detected in DupQualifierFieldNameList.*/
       IF NOT (@HostName IS NULL) PRINT 'The UniqueColName provided (' + @UniqueColName + ') must not exist in DupQualifierFieldNameList (' + @DupQualifierFieldNameList + ').  Other solutions will be sought automatically.'
       SET @UniqueColName = NULL
   END


/*If UniqueColName is provided then perform check to ensure that all the values in that column are, in fact, unique.*/
IF NOT (@UniqueColName IS NULL)
   BEGIN
       SET @SQL = REPLACE(@SQL_DetermineUniqueTemplate,'', @UniqueColName)
       /*Perform a check of this column to determine if all of it's values are unique*/
       EXEC sp_executesql @SQL, N'@SUM as int OUTPUT,@COUNT as int OUTPUT',@SUM OUTPUT,@COUNT OUTPUT
       /*Test to determine if this column contains unique values*/
       If @SUM  @COUNT
           BEGIN
               /*The column specified by UniqueColName does not contain unique values.*/
               IF NOT (@HostName IS NULL) PRINT 'The UniqueColName provided (' + @UniqueColName + ') does not contain unique values.  Other solutions will be sought automatically.'
               SET @UniqueColName = NULL
           END
   END


/*==============================================================*/
/*======================HELP OUTPUT TEXT======================*/
/*==============================================================*/
IF (@TableName IS NULL) OR (@TableName = '/?') OR (@TableName = '?') OR (@DupQualifierFieldNameList IS NULL) OR (@DupQualifierFieldNameList = '/?') OR (@DupQualifierFieldNameList = '?')
   BEGIN
       IF NOT (@HostName IS NULL)
           BEGIN
               PRINT 'sp_RemoveDups ''TableName'', ''DupQualifierFieldNameList'', [''DeleteDups''], [''UniqueColName''], [''CreateIdentColIfNeeded''], '
               PRINT '====================================================================================================================================================================='
               PRINT 'TableName: Required - String - Name of the table to detect duplicate records in.'
               PRINT 'DupQualifierFieldNameList: Required - String - Comma seperated list of columns that make up the unique record within TableName.'
               PRINT 'DeleteDups: Optional - Bit, Set to 0 to delete duplicate records.  A value of NULL or 1 will return the duplicate records to be deleted.'
               PRINT 'UniqueColName: Optional - Bit - A table must have a unique column value in it to perform the deletion logic.  If no UniqueColName is provided then an attemp will be made to locate the RowGUID column.  If that fails then an attempt will be made to locate the Identity column.  If that fails then all of the columns of the table will be examined and the first one with all unique values will be selected.'
               PRINT 'CreateIdentColIfNeeded: Optional - Bit - By default this SP will create an identity column if no unique column can be located.  Pass in a 1 here to run this feature off.'
               PRINT 'StoredProcedureResult: Optional - OUTPUT - Int - Returns a 3 if an error occured, otherwise returns a 0.'
           END
       SET @StoredProcedureResult = 3
       RETURN
   END


/*========================================================================*/
/*======================DETECT USABLE UniqueColName======================*/
/*========================================================================*/
IF @UniqueColName IS NULL
   BEGIN
       /*Check for a RowGUID or Identity column in this table.  If one exists, then utilze it as the unique value for the purposes of this deletion*/
       IF EXISTS(SELECT * FROM SysColumns WHERE ID = Object_ID(@TableName) and ColumnProperty(ID,Name,'IsRowGUIDCol') = 1) SET @UniqueColName =  'RowGUIDCol'
       IF EXISTS(SELECT * FROM SysColumns WHERE ID = Object_ID(@TableName) and ColumnProperty(ID,Name,'IsIdentity') = 1) SET @UniqueColName =  'IdentityCol'

       IF @UniqueColName IS NULL
       /*If no RowGUID or Identity column was found then check all of the columns in this table to see if one of them can be utilized as a unique value column*/
           BEGIN
               /*Select all of the columns from the table in question...*/
               DECLARE MyCursor CURSOR LOCAL SCROLL STATIC FOR SELECT name FROM syscolumns WHERE OBJECT_ID(@TableName)=ID

               OPEN MyCursor
               FETCH NEXT FROM MyCursor INTO @NextColumn
               WHILE @@fetch_status = 0
                   BEGIN
                       /*Create SQL string with correct column name in place.*/
                       SET @SQL = REPLACE(@SQL_DetermineUniqueTemplate,'', @NextColumn)
                       /*Perform a check of this column to determine if all of it's values are unique*/
                       EXEC sp_executesql @SQL, N'@SUM as int OUTPUT,@COUNT as int OUTPUT',@SUM OUTPUT,@COUNT OUTPUT
                       /*Test to determine if this column contains unique values*/
                       If @SUM = @COUNT
                           BEGIN
                               /*A unique values column is detected.  Use it and break out of the loop UNLESS column is specified in DupQualifierFieldNameList*/
                               IF CHARINDEX(@NextColumn, @DupQualifierFieldNameList) = 0
                                   BEGIN
                                       /*NextColumn was NOT detected in DupQualifierFieldNameList, so this is the column we will use.*/
                                       SET @UniqueColName = @NextColumn
                                       BREAK
                                   END
                           END
                       ELSE
                       FETCH NEXT FROM MyCursor INTO @NextColumn
                   END
               CLOSE MyCursor
               DEALLOCATE MyCursor

           END
   END

/*If no UniqueColName has been found then create one UNLESS @CreateIdentColIfNeeded = 1*/
IF (@UniqueColName IS NULL) AND ( (@CreateIdentColIfNeeded IS NULL) OR (@CreateIdentColIfNeeded = 0) )
   BEGIN
       /*Add a sequence column to the table...*/
       IF NOT (@HostName IS NULL) PRINT 'Creating temporary identity column in the ' + @TableName + ' table named ' + @TempIdentColName + ' for use in this ' + LOWER(@ActionText) + ' process...'
       EXEC('ALTER TABLE ' + @TableName + ' ADD ' + @TempIdentColName + ' [int] IDENTITY (1, 1)')
       SET @UniqueColName =  @TempIdentColName
   END


/*============================================================================*/
/*======================EXECUTE DELETION OR SELECTION======================*/
/*===========================================================================*/
IF @UniqueColName IS NULL
   BEGIN
       /*No UniqueColName was provided by the user and none were detected by the script.  This deletion algorythm cannot run.*/
       IF NOT (@HostName IS NULL) PRINT 'Could not perform ' + LOWER(@ActionText) + ' process.  No unique columns were located and the UniqueColName flag is set to 1 (False).'
       SET @StoredProcedureResult = 3
       RETURN
   END
ELSE
   BEGIN
       IF NOT (@HostName IS NULL) PRINT 'Performing ' + LOWER(@ActionText) + ' utilizing the unique values in the ' + @UniqueColName + ' column as a reference...'
       /*
       Create and execute an SQL statement in the form of:

       SELECT * (or DELETE)
           FROM TableName WHERE UniqueColName IN
           (
           SELECT UniqueColName FROM TableName WHERE UniqueColName NOT IN
               (
               SELECT MAX(Cast(UniqueColName AS varchar(36))) FROM TableName GROUP BY DupQualifierFieldNameList, DupQualifierFieldNameList, etc
               )
           )
       */
       /*Delete all duplicate records useing @UniqueColName as a unique ID column */
       IF (@DeleteDups IS NULL) OR (@DeleteDups = 1)
           SET @SQL = 'SELECT * '
       ELSE
           SET @SQL = 'DELETE '

       SET @SQL = @SQL + 'FROM ' + @TableName + ' WHERE ' + @UniqueColName + ' IN '
       SET @SQL = @SQL + CHAR(13) + CHAR(9) + '(' + CHAR(13) + CHAR(9)
       SET @SQL = @SQL + 'SELECT ' + @UniqueColName + ' FROM ' + @TableName  + ' WHERE ' + @UniqueColName + ' NOT IN '
       SET @SQL = @SQL + CHAR(13) + CHAR(9) + CHAR(9) + '(' + CHAR(13) + CHAR(9)+CHAR(9)
       SET @SQL = @SQL + 'SELECT MAX(Cast(' + @UniqueColName + ' AS varchar(36))) FROM '
       SET @SQL = @SQL + @TableName + ' GROUP BY ' + @DupQualifierFieldNameList
       SET @SQL = @SQL + CHAR(13) + CHAR(9) + CHAR(9) + ')' + CHAR(13) + CHAR(9) + ')'

       EXEC (@SQL)
       IF @@ERROR  0
           BEGIN
               IF NOT (@HostName IS NULL) PRINT @ActionText + ' process failed.'
               SET @StoredProcedureResult = 3
           END
       ELSE
           BEGIN
               IF NOT (@HostName IS NULL) PRINT @ActionText + ' completed successfully with this SQL: ' + CHAR(13) + @SQL
               SET @StoredProcedureResult = 0
           END
   END


IF (@UniqueColName = @TempIdentColName) AND ( (@CreateIdentColIfNeeded IS NULL) OR (@CreateIdentColIfNeeded = 0) )
   BEGIN
       /*Remove the sequence column from the table...*/
       IF NOT (@HostName IS NULL) PRINT 'Removing temporary identity column named ' + @TempIdentColName + ' from the ' + @TableName + ' table...'
       EXEC('ALTER TABLE ' + @TableName + ' DROP COLUMN ' + @TempIdentColName)
   END

GO


/*
USAGE

sp_RemoveDups 'TableName', 'DupQualifierFieldNameList', ['DeleteDups'], ['UniqueColName'], ['CreateIdentColIfNeeded'], 
================================================================================================================================================
TableName: Required - String - Name of the table to detect duplicate records in.
DupQualifierFieldNameList: Required - String - Comma seperated list of columns that make up the 
unique record within TableName.
DeleteDups: Optional - Bit, Set to 0 to delete duplicate records. A value of NULL or 1 will 
return the duplicate records to be deleted.
UniqueColName: Optional - Bit - A table must have a unique column value in it to perform the 
deletion logic. If no UniqueColName is provided then an attemp will be made to locate 
the RowGUID column. If that fails then an attempt will be made to locate the 
Identity column. If that fails then all of the columns of the table will be examined 
and the first one with all unique values will be selected.
CreateIdentColIfNeeded: Optional - Bit - By default this SP will create an identity column if 
no unique column can be located. Pass in a 1 here to run this feature off.
StoredProcedureResult: Optional - OUTPUT - Int - Returns a 3 if an error occured, otherwise returns a 0.

Simple Syntax:
Use [databaseName]
sp_RemoveDups '[tableName]','[uniqueColName]','[Optional bit flag - set to zero to remove dups, omit to report only]'
*/