Is there any limitation of nested select.

Is there any limitation of nested select.If yes please let me know.

Hi,
There are no practical limits to nested SELECTs, but as other repliers have already pointed out they quickly become a performance hog. I have stopped using them for years, and when I teach ABAP performance classes I also quote them as one of the top "don'ts". With nested selects, the number of calls to the DBMS can easily become enormous, putting the database server under stress.
A good alternative - the one I favour most myself - is to use SELECT INTO TABLE for the"outer" select, followed by appropriate SELECT FOR ALL ENTRIES statements to handle the inner levels.
ABAP joins are another alternative. When properly written, a join will be faster than a nested select. The problem is however that very often joins are not properly written. SELECT statements should always respect the KISS principle (keep it simple, stupid) and with a join it is very easy to violate that rule. A join over 2 tables should probably be OK, but with 3 or more tables you want to be very careful. If you really want to code a complex join, I recommend that you also code the same logic with different means (INTO TABLE/FOR ALL ENTRIES or even nested selects) and then compare that with the join. By the way: don't just compare the performance, also make sure that the two return the same data. You wouldn't be the first to code a really fast join which unfortunately returns incorrect results.

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