> SELECT cmp.WELL_INDEX, cmp.COMPOUND, con.CONCENTRATION
> FROM SCR_WELL_COMPOUND cmp, SCR_WELL_CONCENTRATION con
> WHERE cmp.BARCODE=con.BARCODE
> AND cmp.WELL_INDEX=con.WELL_INDEX
> AND cmp.MAT_ID=con.MAT_ID
> AND cmp.MAT_ID = 3
> AND cmp.BARCODE='910125864'
> AND cmp.ID_LEVEL = 1;
Quick guess - type mismatch forcing sequential scan. Try some quotes:
AND cmp.MAT_ID = '3'
AND cmp.BARCODE='910125864'
AND cmp.ID_LEVEL = '1';
M