A different approach to using a SQL cursors in SP? - sql

Question

I am writing a stored procedure in SQL and I am currently in the position of having 3 nested cursors (which isn;t running quite how I would like). I'd appreciate any suggestions on how I can break out of the cursor is the solution trap
I basically have 2 tables (both temporary during the SP populated by SELECT statements from the application)
1 - A list of tables, columns and datatypes
Table1 | SURNAME | VARCHAR
| SEX | VARCHAR
| DOB | DATETIME
------------------------------
Table2 | ADDRESS | VARCHAR
------------------------------
Table3 | SALARY | INT
------------------------------
Table4 | USERNAME | VARCHAR
| PASSWORD | VARCHAR
2 - A one column list of user numbers
My application has to loop through each user number, then for each user I have to loop through the distinct tables (Table1, Table2, Table3, Table4) and see if there is any data in that tabel for that user (using dyanmic SQL so I can pass the table name as a parameter). If there is, I then have to then loop through each column that relates to that table and build a dynamic SQL INSERT statement
So for user number 2...
any data in Table1? No - skip
any data in Table2? Yes - copy rows into temp table then build dynamic SQL for ADDRESS value
any data in Table3? No - skip
any data in Table4? Yes - copy rows into temp table then build dynamic SQL for USERNAME and PASSWORD columns
The cursor approach works fine from a functionality point of view but performance is a little slow. I've made sure the 2 source tables are as tight as possible, when creating my dynamic SQL I copy the relevant rows only into a temp table to process, I've made my cursors FAST_FORWARD and READ_ONLY
Is there any approach I can take instead?
ORIGINAL CODE POSTED AS REQUESTED:
IF OBJECT_ID('tempdb..##MembersToDelete') IS NOT NULL DROP TABLE ##MembersToDelete
IF OBJECT_ID('tempdb..##TempDataTable') IS NOT NULL DROP TABLE ##TempDataTable
DELETE FROM #CompSetTable
DELETE FROM DataRefreshDeletes
DELETE FROM DataRefreshInserts
--BUILD THE INDIVIDUAL SELECT STATEMENTS INTO A TEMP TABLE
SET #RowPosition = 1;
SET #inSelectFilter = #inSelectFilter + ';';
SET #inSelectFilter = REPLACE(#inSelectFilter,'/','''');
WHILE LEN(#inSelectFilter) > 0
BEGIN
IF PATINDEX('%;%',#inSelectFilter) > 0
BEGIN
SET #SelectParameter = SUBSTRING(#inSelectFilter, 0, PATINDEX('%;%',#inSelectFilter))
SET #inSelectFilter = SUBSTRING(#inSelectFilter, LEN(#SelectParameter + ';') + 1,LEN(#inSelectFilter))
IF #RowPosition = 1
BEGIN
INSERT INTO #SelectParameterTable VALUES ('WHERE ' + #SelectParameter)
END
ELSE
BEGIN
INSERT INTO #SelectParameterTable VALUES (' AND ' + #SelectParameter)
END
SET #RowPosition = #RowPosition + 1
END
ELSE
BEGIN
SET #SelectParameter = #inSelectFilter
SET #inSelectFilter = NULL
END
END
--BUILD THE COMPLETE DELETE STATEMENT
SET #SelectParameter = NULL;
SELECT #SelectParameter = COALESCE(#SelectParameter, '') + statementString FROM #SelectParameterTable
--INSERT THE MEMBER NUMBERS INTO THE TEMP TABLE
IF OBJECT_ID('tempdb..##MembersToDelete') IS NOT NULL DROP TABLE ##MembersToDelete
SET #SelectParameter = 'SELECT MEMBNO INTO ##MembersToDelete FROM BASIC ' + #SelectParameter
BEGIN TRY
EXECUTE sp_executesql #SelectParameter
END TRY
BEGIN CATCH
Print 'The following statement could not be run - please check the syntax...'
Print #SelectParameter
GOTO cleanUpAndFinish
END CATCH
SELECT #MembersToDeleteCount = COUNT(*) FROM ##MembersToDelete
Print '##MembersToDelete TABLE BUILT - ' + CONVERT(VARCHAR(26), GETDATE(), 109)
--BUILD LIST OF COMPENDIA TABLES (ORDERED BY DSET)
DELETE FROM #CompSetTable
INSERT INTO #CompSetTable SELECT d.DSNAME, c.column_name, d.DSET, c.data_type FROM DICTIONARY d, INFORMATION_SCHEMA.COLUMNS c WHERE DNUM = -1 AND DSET < 250 AND c.table_name = d.DSNAME ORDER BY d.DSET
Print '#CompSetTable TABLE BUILT - ' + CONVERT(VARCHAR(26), GETDATE(), 109)
DECLARE setInsertCursor CURSOR GLOBAL FAST_FORWARD READ_ONLY FOR SELECT DISTINCT setName, setNumber FROM #CompSetTable ORDER BY setNumber
--WE NOW HAVE THE LIST OF MEMBER NUMBERS AND THE LIST OF TABLES TO BUILD THE DELETE STATEMENT
SELECT #MemberNumberString = COALESCE(#MemberNumberString + ', ', '') + LTRIM(STR(MEMBNO)) FROM ##MembersToDelete
DECLARE setDeleteCursor CURSOR READ_ONLY SCROLL FOR SELECT DISTINCT setName, setNumber FROM #CompSetTable ORDER BY setNumber
OPEN setDeleteCursor
FETCH LAST FROM setDeleteCursor INTO #SetName, #SetNumber
WHILE ##FETCH_STATUS = 0
BEGIN
INSERT INTO #DeleteStatementTable VALUES ('DELETE FROM ' + UPPER(#SetName) + ' WHERE MEMBNO IN (' + #MemberNumberString + ')')
FETCH PRIOR FROM setDeleteCursor INTO #SetName, #SetNumber
END
CLOSE setDeleteCursor
DEALLOCATE setDeleteCursor
Print '#DeleteStatementTable TABLE BUILT - ' + CONVERT(VARCHAR(26), GETDATE(), 109)
DECLARE memberInsertCursor CURSOR FOR SELECT MEMBNO FROM ##MembersToDelete
OPEN memberInsertCursor
FETCH NEXT FROM memberInsertCursor INTO #MemberNumber
WHILE ##FETCH_STATUS = 0
BEGIN
--NOW BUILD THE INSERT STATEMENTS
OPEN setInsertCursor
FETCH NEXT FROM setInsertCursor INTO #SetName, #SetNumber
WHILE ##FETCH_STATUS = 0
BEGIN
--CHECK IF MEMBER HAS ANY ROWS IN THIS SET - IF NOT, SKIP
SET #ROWCOUNT = 0
SELECT #COUNTSQL = N'SELECT #countOUT = COUNT(*) FROM ' + #SetName + ' WHERE MEMBNO = ' + LTRIM(STR(#MemberNumber))
EXEC sp_executesql #COUNTSQL, N'#countOUT INT OUTPUT', #countOUT=#ROWCOUNT OUTPUT;
IF #ROWCOUNT = 0
BEGIN
GOTO nextSet
END
SET #VALUES = NULL;
--DROP TEMPORARY TABLE
IF OBJECT_ID('tempdb..##TempDataTable') IS NOT NULL DROP TABLE ##TempDataTable
--POPULATE TEMPORARY TABLE
SET #SQL = 'SELECT * INTO ##TempDataTable FROM ' + #SetName + ' WHERE MEMBNO = ' + LTRIM(STR(#MemberNumber))
EXECUTE sp_executesql #SQL
--BUILD SELECT STATEMENT
SET #INSERTSTRING = NULL
SET #INSERTSTRING = CAST('' as nVarChar(MAX)) + 'SELECT ''INSERT INTO ' + #SetName + ' VALUES ('''
DECLARE setColumnCursor CURSOR FAST_FORWARD READ_ONLY FOR SELECT columnName, dataType FROM #CompSetTable WHERE setName = #SetName
OPEN setColumnCursor
FETCH NEXT FROM setColumnCursor INTO #ColumnName, #DataType
WHILE ##FETCH_STATUS = 0
BEGIN
IF #DataType IN ('text','varchar','nvarchar','ntext','char')
BEGIN
SET #INSERTSTRING = CAST('' as nVarChar(MAX)) + #INSERTSTRING + ''''' + ISNULL(' + #ColumnName + ',''NULL'') + '''''','''
END
ELSE IF #DataType IN ('int','decimal','smallint','numeric','tinyint','bigint','float')
BEGIN
--SET #INSERTSTRING = #INSERTSTRING + ' + ' + #COLUMNNAMENULL + ' + '','''
SET #INSERTSTRING = CAST('' as nVarChar(MAX)) + #INSERTSTRING + ' + ISNULL(CONVERT(VARCHAR(MAX),' + #ColumnName + '),''NULL'')' + ' + '','''
END
ELSE IF #DataType IN ('datetime')
BEGIN
--SET #INSERTSTRING = #INSERTSTRING + ' + ' + #COLUMNNAMENULL + ' + '','''
SET #INSERTSTRING = CAST('' as nVarChar(MAX)) + #INSERTSTRING + ''''' + ISNULL(CONVERT(VARCHAR(MAX),' + #ColumnName + '),''NULL'')' + ' + '''''','''
END
FETCH NEXT FROM setColumnCursor INTO #ColumnName, #DataType
END
CLOSE setColumnCursor
DEALLOCATE setColumnCursor
SET #INSERTSTRING = #INSERTSTRING + '+'')'''
SET #INSERTSTRING = #INSERTSTRING + ' FROM ##TempDataTable'
INSERT INTO #InsertStatementTable EXECUTE sp_executesql #INSERTSTRING
nextSet:
FETCH NEXT FROM setInsertCursor INTO #SetName, #SetNumber
END
FETCH NEXT FROM memberInsertCursor INTO #MemberNumber
END
CLOSE memberInsertCursor
DEALLOCATE memberInsertCursor
CLOSE setInsertCursor
DEALLOCATE setInsertCursor

Answer 1

Maybe I didn't follow your question correctly but what's wrong with using 'insert...select' where the select joins all these tables?

Answer 2

It sounds like you are trying to implement precedence. I question whether you actually need the original table. If not, just use not exists
insert into . . .
select . . .
from Table1;
insert into . . .
select . . .
from Table2
where not exists (select 1
from Table1
where Table1.userid = Table2.userid and
Table1.colname = Table2.colname
);
insert into . . .
select . . .
from Table3
where not exists (select 1
from Table1
where Table1.userid = Table3.userid and
Table1.colname = Table3.colname
) and
not exists (select 1
from Table2
where Table2.userid = Table3.userid and
Table2.colname = Table3.colname
);
If you are actually conditionally choosing the columns from each table, then you might have to construct the above as dynamic SQL.

Answer 3

If you add ID columns in each table and index it you can make selection a lot faster. Give unique index for ID column and that's it. You can improve the speed of entire action a lot.