Question

我有这个问题：

SELECT * FROM `employee_activities` a
LEFT JOIN `activity` b ON a.activity_code = b.code
LEFT JOIN `employees` c ON a.employee_code = c.code
WHERE b.type = "Design"
AND c.code NOT IN(
    SELECT * FROM `employee_activities` a
        LEFT JOIN `activity` b ON a.activity_code = b.code
        LEFT JOIN `employees` c ON a.employee_code = c.code
        WHERE b.type = "Testing"
)
GROUP BY c.code

我收到此错误：

#1241 - Operand should contain 1 column(s)

我想要让所有至少有一项活动类型为“设计”的员工和没有“测试”类型活动的员工。

我有一个有效的查询，但我希望它能用于连接。

这有效：

SELECT c.name FROM `employee_activities` a, `activity` b, `employees` c
WHERE a.activity_code = b.code
AND a.employee_code = c.code
AND b.type = "Design"

AND c.code NOT IN(
    SELECT c.code FROM `employee_activities` a, `activity` b, `employees` c
        WHERE a.activity_code = b.code
        AND a.employee_code = c.code
        AND b.type = "Testing"
)
GROUP BY c.code

我在带连接的sql上做错了什么？

Answer 1

对于不在子查询中 - 它应该只包含一列 - 例如

SELECT * FROM `employee_activities` a
LEFT JOIN `activity` b ON a.activity_code = b.code
LEFT JOIN `employees` c ON a.employee_code = c.code
WHERE b.type = "Design"
AND c.code NOT IN(
    SELECT b.employee_code FROM `employee_activities` a
        LEFT JOIN `activity` b ON a.activity_code = b.code
        LEFT JOIN `employees` c ON a.employee_code = c.code
        WHERE b.type = "Testing"
)
GROUP BY c.code

Answer 2

您的查询

AND c.code NOT IN(
   SELECT * FROM `employee_activities` a
...

尝试将c.code与子查询中的所有列进行比较。你想要的可能是什么;

AND c.code NOT IN(
    SELECT c.code FROM `employee_activities` a

此外，您的LEFT JOIN;

出现问题

LEFT JOIN `activity` b ON a.activity_code = b.code
...
WHERE b.type = "Design"

当您将左边加入的列与WHERE子句进行比较时，它基本上将整个连接转换为INNER JOIN。由于您的原始查询似乎使用内部联接，这应该没问题，但您也可以将其更改为;

SELECT * FROM `employee_activities` a
JOIN `activity` b ON a.activity_code = b.code AND b.type='Design'
LEFT JOIN `employees` c ON a.employee_code = c.code

Answer 3

你的问题在于这一部分：

AND c.code NOT IN(
SELECT * FROM

你不能在这里查看c.code是否在返回的字段值列表中，并且必须在select中指定一个字段。

Answer 4

问题出在本节：

AND c.code NOT IN( 
    SELECT * FROM `employee_activities` a

您无法在该嵌套查询中SELECT *。您需要选择一个与c.code进行比较的列。你需要这个：

AND c.code NOT IN( 
    SELECT c.code FROM `employee_activities` a

Answer 5

做到这一点：

SELECT * FROM `employee_activities` a
LEFT JOIN `activity` b ON a.activity_code = b.code
LEFT JOIN `employees` c ON a.employee_code = c.code
WHERE b.type = "Design"
AND c.code NOT IN(
    SELECT c.code FROM `employee_activities` a
        LEFT JOIN `activity` b ON a.activity_code = b.code
        LEFT JOIN `employees` c ON a.employee_code = c.code
        WHERE b.type = "Testing"
)
GROUP BY c.code

在此处，您应该将数据与代码列进行比较，*将获取所有记录。

在查询中使用联接时出错

5 个答案: