Avoiding Cursor in SQL - sql-server

Question

What is the best alternative to using a cursor in SQL if I am suffering from performance issues ?
I got the following code wherein it uses Cursor to loop through and insert records.
DECLARE #AuditBatchID_logRow INT,
#AuditOperationID_logRow INT,
#RowIdentifier_logRow nvarchar(200),
#AuditDBTableID_logRow INT,
#AuditLogRowID INT,
#AuditDBColumnID INT,
#NewValue nvarchar(200),
#PreviousVaue nvarchar(200),
#NewDisplayValue nvarchar(200)
DECLARE Crsr_AUDITLOGROW CURSOR LOCAL FORWARD_ONLY STATIC
FOR
SELECT [t0].[AuditBatchID],
[t1].[AuditOperationID],
[t1].[RowIdentifier],
[t0].[AuditTableID],
[t1].[AuditLogRowID]
FROM [AuditBatchTable] AS [t0]
INNER JOIN [AuditLogRow] AS [t1]
ON [t0].[AuditBatchTableID] = [t1].[AuditBatchTableID]
Open Crsr_AUDITLOGROW
FETCH NEXT FROM Crsr_AUDITLOGROW
INTO #AuditBatchID_logRow,
#AuditOperationID_logRow,
#RowIdentifier_logRow,
#AuditDBTableID_logRow,
#AuditLogRowID
While(##FETCH_STATUS = 0)
BEGIN
INSERT INTO AuditLog(AuditLogRowID, AuditColumnID,
NewValue, OldDisplayValue, NewDisplayValue)
(SELECT #AuditLogRowID,
[ac].[AuditColumnID],
[t0].[UserEnteredValue],
[t0].[PreviousDisplayValue],
[t0].[DisplayValue]
FROM FMG_PROD.dbo.AuditLog AS [t0]
INNER JOIN FMG_PROD.dbo.AuditDBColumn AS [t1]
ON [t0].[AuditDBColumnID] = [t1].[AuditDBColumnID]
INNER JOIN FMG_PROD.dbo.AuditDBTable AS [t2]
ON [t1].[AuditDBTableID] = [t2].[AuditDBTableID]
INNER JOIN AuditTable AS [AT]
ON [t2].AuditDBTable = [AT].AuditTable
INNER JOIN AuditColumn AS [AC]
ON [AT].AuditTableID = [AC].AuditTableID
WHERE
([t0].[AuditBatchID] = #AuditBatchID_logRow)
AND ([t0].[AuditOperationID] = #AuditOperationID_logRow)
AND ([AT].[AuditTableID] = #AuditDBTableID_logRow)
AND [AC].AuditColumn = [t1].AuditDBColumn
AND (#RowIdentifier_logRow =
CASE ISNUMERIC(#RowIdentifier_logRow)
WHEN 1 then
CAST ([t0].[RowID] AS VARCHAR(200))
ELSE
CAST([t0].[RowGUID] AS VARCHAR(200))
END))
FETCH NEXT FROM Crsr_AUDITLOGROW
INTO #AuditBatchID_logRow,
#AuditOperationID_logRow,
#RowIdentifier_logRow,
#AuditDBTableID_logRow,
#AuditLogRowID
END
CLOSE Crsr_AUDITLOGROW
DEALLOCATE Crsr_AUDITLOGROW

Answer 1

Well, you're thinking and coding like a structured programmer - linearly, one by one, in tighest control of the program flow. That's how we (almost) all have been thought to program.
You need to think like a SQL guy - in SETS of data (not single rows, one at a time).
Avoid the need to tightly control each step of the algorithm - instead, just tell SQL Server WHAT you want - not HOW to do each step!
In the end, you're inserting a bunch of rows into the AuditLog table. Why do you need a cursor for that??
INSERT INTO AuditLog(...list of columns.....)
SELECT (....list of columns....)
FROM Table1
INNER JOIN ..........
INNER JOIN .........
WHERE ........
and you're done! Define what you want inserted into the table - DO NOT tell SQL Server in excrutiating detail how to do it - it'll know very well, thank you!
Marc