Oracle PL/SQL:两个表之间的count(*)

Question

尝试计算2个表之间的计数差异.

跟着这个回答但是得到了00923. 00000 - "FROM keyword not found where expected"

SELECT ( SELECT count(*) FROM XE_ERR_OVLP WHERE FLAG = 'E') 
- (SELECT count(*) FROM XE_ERR_RANG WHERE FLAG = 'H' ) as cnt;

怎么能实现这一目标？

Answer 1

那是:

SELECT ( SELECT count(*) FROM XE_ERR_OVLP WHERE FLAG = 'E') 
  - (SELECT count(*) FROM XE_ERR_RANG WHERE FLAG = 'H' ) as cnt 
  from dual;

与其他数据库相反,Oracle需要一个from子句.您可以使用虚拟表dual.