Oracle SQL "not in" statement optimization, query a table has, B table does not have data

In the case of a large record, the not in query will certainly be slow and unacceptable. Like what:

SELECT A.*  fromWHERE A.user_id not in (SELECT B.user_id from Table_b)

the best way to find it now is to check it in seconds. For example, query the DEPT_ID data with table A and b not available:

SELECT A.*from  tb_dept A, Tb_dept_lev BWHERE= b.dept_id (+)  and  is NULL

The (+) number can be understood as: + is added, which table has a plus sign, and this table is the matching table. Here the plus sign is written in the right table, the left table is all displayed, so it is left connected.

Original: http://blog.csdn.net/dengjh_business/article/details/35226227

Oracle SQL "not in" statement optimization, query a table has, B table does not have data