2

我有一个由 COALESCE 语法组成的查询。COALESCE 语法只是查找文件的审核日期。在我的 WHERE 语句中，我只想从AuditDate别名字段输出已审核的文件库，但我不起作用。这是我的查询。

SELECT COALESCE(qua.starttime, prd.starttime) AS `AuditDate`,
       prd.employeeno AS `EmployeeNo`,
       prd.starttime AS `StartTime`,
       prd.endtime AS `EndTime`
  FROM production prd
  LEFT JOIN qualityaudit qua
    ON prd.id=qua.id
 WHERE `AuditDate` BETWEEN '2011-10-01 00:00:00' AND '2011-10-01 23:59:59';

任何人都可以帮助我如何让这个查询正确吗？

4

4 回答 4

3

您的查询需要是这样的

SELECT COALESCE(qua.starttime, prd.starttime) AS `AuditDate`,
       prd.employeeno AS `EmployeeNo`,
       prd.starttime AS `StartTime`,
       prd.endtime AS `EndTime`
  FROM production prd
  LEFT JOIN qualityaudit qua
    ON prd.id=qua.id
 WHERE COALESCE(qua.starttime, prd.starttime) BETWEEN '2011-10-01 00:00:00' AND '2011-10-01 23:59:59';

对于您的情况，您不能使用来自函数结果的别名作为WHERE子句中的查询条件（请参阅http://dev.mysql.com/doc/refman/5.0/en/problems-with-alias.html）。但是您可以使用别名来搜索 inHAVING子句，如 MySQL 5.0.2 和更高版本的 permitHAVING子句来引用 SELECT 列表或外部子查询中的 select_expr 中命名的任何列或别名，并聚合函数，例如

SELECT COALESCE(qua.starttime, prd.starttime) AS `AuditDate`,
       prd.employeeno AS `EmployeeNo`,
       prd.starttime AS `StartTime`,
       prd.endtime AS `EndTime`
  FROM production prd
  LEFT JOIN qualityaudit qua
    ON prd.id=qua.id
 HAVING `AuditDate` BETWEEN '2011-10-01 00:00:00' AND '2011-10-01 23:59:59';

两者都有相同的结果

于 2011-10-10T11:33:30.370 回答
2

采用

SELECT COALESCE(qua.starttime, prd.starttime) AS `AuditDate`,
       prd.employeeno AS `EmployeeNo`,
       prd.starttime AS `StartTime`,
       prd.endtime AS `EndTime`
  FROM production prd
  LEFT JOIN qualityaudit qua
    ON prd.id=qua.id
 WHERE COALESCE(qua.starttime, prd.starttime) BETWEEN '2011-10-01 00:00:00' AND '2011-10-01 23:59:59';

以上假设您的日期格式/列类型确实匹配......

于 2011-10-10T11:33:01.430 回答
2

您不能像其他人指出的那样使用别名。为避免两次调用 coalesce，您可以使用 HAVING 语句。

SELECT COALESCE(qua.starttime, prd.starttime) AS `AuditDate`,
       prd.employeeno AS `EmployeeNo`,
       prd.starttime AS `StartTime`,
       prd.endtime AS `EndTime`
  FROM production prd
  LEFT JOIN qualityaudit qua
    ON prd.id=qua.id
HAVING `AuditDate` BETWEEN '2011-10-01 00:00:00' AND '2011-10-01 23:59:59';
于 2011-10-10T11:35:51.903 回答
1

您不能使用子句SELECT列表中的别名。WHERE

用这个：

SELECT *
FROM
  ( SELECT COALESCE(qua.starttime, prd.starttime) AS `AuditDate`,
           prd.employeeno AS `EmployeeNo`,
           prd.starttime AS `StartTime`,
           prd.endtime AS `EndTime`
      FROM production prd
      LEFT JOIN qualityaudit qua
        ON prd.id=qua.id
  ) AS tmp
WHERE `AuditDate` BETWEEN '2011-10-01 00:00:00' AND '2011-10-01 23:59:59';

或复制代码：

SELECT COALESCE(qua.starttime, prd.starttime) AS `AuditDate`,
       prd.employeeno AS `EmployeeNo`,
       prd.starttime AS `StartTime`,
       prd.endtime AS `EndTime`
  FROM production prd
  LEFT JOIN qualityaudit qua
    ON prd.id=qua.id
 WHERE COALESCE(qua.starttime, prd.starttime) 
         BETWEEN '2011-10-01 00:00:00' AND '2011-10-01 23:59:59';
于 2011-10-10T11:33:53.380 回答