NOTIN使用注意事項

下午被一條SQL折磨了
select EMP_ID,EMP_NUM,NAME
 from employee 
 WHERE 
 emp_id in
 (
 select distinct E.emp_id
 from EMPLOYEE E 
 INNER JOIN PROJECT_EMPLOYEE pe on e.emp_id = pe.emp_id
 INNER JOIN PROJECT p on pe.pro_id = p.pro_id
 where pe.pro_id ='B49CBE19481447A68445461E7BE02B13'
 );//3條數(shù)據(jù)
因為業(yè)務(wù)上有變更，需要在此SQL基礎(chǔ)上加上一些其他限制，修改后的SQL：
select EMP_ID,EMP_NUM,NAME
 from employee 
 WHERE 
 emp_id in
 (
 select distinct E.emp_id
 from EMPLOYEE E 
 INNER JOIN PROJECT_EMPLOYEE pe on e.emp_id = pe.emp_id
 INNER JOIN PROJECT p on pe.pro_id = p.pro_id
 where pe.pro_id ='B49CBE19481447A68445461E7BE02B13'
 and e.emp_id not in (select s.emp_id from salesteam s )
 );//0條數(shù)據(jù)，把not in 改成in有1條數(shù)據(jù)
糾結(jié)很久，發(fā)現(xiàn)是因為not in 后面的查詢條件select s.emp_id from salesteam s所返回的數(shù)據(jù)中存在null的原因

解決辦法就是將not in的子查詢中加上is not null的條件
select s.emp_id from salesteam s where s.emp_id is not null