Tag Archives: Oracle
Performance differences between IN and EXISTS
Very often I hear people wondering if it’s better the EXISTS or the IN operator. Let’s start by saying that the two operators behave differently when NULL values are involved (see this post). If you are sure that the field … Continue reading
NOT IN vs. NOT EXISTS when NULL values are involved
NOT IN does not behave as you would expect when NULL values are involved. Suppose you have the following tables: TABLE_A CD_FIELD DS_FIELD 1 ALPHA 2 BETA TABLE_B CD_FIELD DS_FIELD 1 GAMMA NULL DELTA Now try the following query: SELECT … Continue reading
