>>Hi,
>>
>>What is a better practice and more efficient when using a derived table in a SQL Select:
>>
>>
>>select Table1.* T1 where exists (select * from Table2 T2 where T1.pk_fld = T2.pk_fld and T2.fld2 = '123')
>>
>>
>>vs
>>
>>
>>select Table1.* T1 where T1.pk_fld in (select pk_fld from Table2 T2 where T1.pk_fld = T2.pk_fld and T2.fld2 = '123')
>>
>>
>>TIA
>
>I prefer using EXISTS because of the possible NULL problem with IN syntax.
>
>BTW, your IN is not correct. You don't need to use correlated fields in IN condition, e.g. this would be correct:
>
>
>select Table1.* T1 where T1.pk_fld in (select pk_fld from Table2 T2 where T2.fld2 = '123')
>
Thank you.
In terms of correcting my syntax, are you saying that the derived query will automatically only use records of PK_FLD equal to PK_FLD in Table1?
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