Question

我做错了什么？如果更多的人单身而不是已婚，则需要显示是，如果反之，则不需要。我只想让它显示是或否。

IF
select COUNT(StudMaritalStatus) from students WHERE StudMaritalStatus = "M"
<
select COUNT(StudMaritalStatus) from students WHERE StudMaritalStatus = "S"
Print 'Yes'
ELSE
Print 'No';

Answer 1

考虑到MySQL使用：

 IF expression THEN
      expression        
    ELSE
 ENDIF;

你最好不要使用select语句

DECLARE married int, single int

SET married = select COUNT(StudMaritalStatus) from students WHERE StudMaritalStatus = 'M'

SET single = select COUNT(StudMaritalStatus) from students WHERE StudMaritalStatus = 'S'

IF married < single THEN 
  PRINT 'YES'
ELSE 
  PRINT 'NO'
END IF

回答是的，你的语法错了 https://dev.mysql.com/doc/refman/5.7/en/if.html

Answer 2

你想要这样的东西：

select case when married >= single then 'M' else 'S' end
from 
(
select sum(case when StudMaritalStatus = 'M' then 1 else 0 end) married
, sum (case when StudMaritalStatus = 'S' then 1 else 0 end) single
from students
) derivedTable

打破交易取决于您的业务需求，我们都不知道。

带有打印的SQL IF语句

2 个答案: