Delete query working very slow

[jaryszek]

Hi Guys,

i have a delete query wtih this code:

DELETE tbl_Employees_SAP.*FROM tbl_Employees_SAP
WHERE (((tbl_Employees_SAP.SAP_Nr) Not In (SELECT tbl_temp_SAP_pr.SAP_Nr FROM tbl_temp_SAP_pr)));

both these tables have about 25 000 thousends records.
These query is working very very slow i do not why.
If i do this operationas on my smaller tables - it is working like a charm...

why ?

Best Wishes,
Jacek Antek

[jaryszek]

Okey,

If have change a little my SQL code into:

DELETE *FROM tbl_Employees_SAP
WHERE SAP_Nr  in (Select SAP_Nr From QryDeleteSAPFirst);

where QryDeleteSAPFirst is a separated query :

SELECT tbl_Employees_SAP.SAP_NrFROM tbl_Employees_SAP LEFT JOIN tbl_temp_SAP_pr ON tbl_Employees_SAP.SAP_Nr = tbl_temp_SAP_pr.SAP_Nr
WHERE (((tbl_temp_SAP_pr.SAP_Nr) Is Null));

Now the query run very fast - 1 second and all not necessay rows are deleted...

Best Wishes,
Jacek