Author: Builder.com
Thursday, October 14 2004 12:00 PM
From the surface, IN and EXITS SQL statements are interchangeable and equivalent. However, they will have great differences in handling UULL data, and result in different results. The root of the problem is in an Oracle database, a NULL value means unknown variables, so the result of the comparison function of the operation NULL value is also an unknown variable, and the value returns NULL is usually ignored. For example, the following queries will not return a row of values:
