Question

我遇到选择案例的问题..

表格

模板（temp_id，temp_title，temp_applyto，temp_status，start_date，end_date）


[其中temp_apply存储int 1-individu，2-branch，3-dept和4-position]




individu （applyto_id，applyto_individu，applyto_temp）



分支（applyto_id，applyto_branch，applyto_temp）



dept （applyto_id，applyto_dept，applyto_temp）



职位（applyto_id，applyto_position，applyto_temp）



员工（身份证，姓名，分支机构，部门，职位）

递减：

我想检查用户他是否在个人，分支，部门或职位。如果 temp_applyto（表格模板）= 1 ，那么我想检查表 individu 如果用户存在，如果 temp_applyto = 2 那么我想要检查表分支，如果用户存在且同样继续。

到目前为止的查询：

SELECT (CASE WHEN temp_applyto=1 
    THEN (SELECT applyto_temp FROM individu 
          WHERE applyto_individu=$user)
    WHEN temp_applyto=2 
    THEN (SELECT a.applyto_temp FROM branch a, staff b 
          WHERE >a.applyto_branch=b.branch AND b.id=$user) 
    WHEN temp_applyto=3 
    THEN (SELECT a.applyto_temp FROM dept a, staff b 
          WHERE >a.applyto_dept=b.dept AND b.id=$user) 
    WHEN temp_applyto=4 THEN (SELECT a.applyto_temp FROM position a, staff b 
          WHERE a.applyto_position=b.position AND b.id=$user) 
    ELSE 0 end) as template_temp 
FROM template 
WHERE '2013-08-21' BETWEEN start_date AND end_date

我收到此错误：子查询返回超过1行

Answer 1

错误很明显，因为我们的一个子查询返回了多行。您可以在每个子查询上使用LIMIT 1。但是，如果您想获得多行，可以使用UNION这样的

SELECT template_temp FROM
(
    (SELECT applyto_temp AS template_temp, 1 AS temp_applyto FROM individu WHERE applyto_individu = $user) UNION
    (SELECT a.applyto_temp AS template_temp, 2 AS temp_applyto FROM branch a, staff b WHERE a.applyto_branch=b.branch AND b.id=$user) UNION
    (SELECT a.applyto_temp AS template_temp, 3 AS temp_applyto FROM dept a, staff b WHERE a.applyto_dept=b.dept AND b.id=$user) UNION
    (SELECT a.applyto_temp AS template_temp, 4 AS temp_applyto FROM `position` a, staff b WHERE a.applyto_position=b.`position` AND b.id=$user)
) AS combine INNER JOIN template
ON (combine.temp_applyto = template.temp_applyto)
WHERE '2013-08-21' BETWEEN start_date AND end_date

Answer 2

错误是不言自明的：您的一个子查询返回多行。有几种方法可以解决您的问题。一个简单的方法是将LIMIT 1添加到每个子选择中。或者，您可以选择行数 - 然后将结果与0进行比较：

SELECT (CASE WHEN temp_applyto=1 
    THEN (SELECT COUNT(*) FROM individu 
          WHERE applyto_individu=$user)
    WHEN temp_applyto=2 
    THEN (SELECT COUNT(*) FROM branch a, staff b 
          WHERE >a.applyto_branch=b.branch AND b.id=$user)
    WHEN temp_applyto=3 
    THEN (SELECT COUNT(*) FROM dept a, staff b 
          WHERE >a.applyto_dept=b.dept AND b.id=$user) 
    WHEN temp_applyto=4
    THEN (SELECT COUNT(*) FROM position a, staff b 
          WHERE a.applyto_position=b.position AND b.id=$user)
    ELSE 0 END) as template_temp 
FROM template
WHERE '2013-08-21' BETWEEN start_date AND end_date

这将返回一个数字 - 如果没有匹配则为0，如果没有则匹配数量。

mysql查询选择案例多于1个表

2 个答案: