在子查询中选择多行或者回避子查询

Question

我想知道如何实现查询选择按clientid列分组的时间列的列WHERE子句除以月份和部门来自同一个表：

表格如下：

这里的目标是获得如下最终结果：

结果1.0

SELECT t.clientid, t.department, 
                        (SELECT SEC_TO_TIME( SUM( TIME_TO_SEC( `time` ) ) ) FROM time_management WHERE YEAR(date)='$year' AND MONTH(date)= 12 AND department = '$department' GROUP by clientid  ) as january,
                        (SELECT SEC_TO_TIME( SUM( TIME_TO_SEC( `time` ) ) ) FROM time_management WHERE YEAR(date)='$year' AND MONTH(date)= 2 AND department = '$department' GROUP by clientid ) as february
                        FROM time_management t WHERE t.department = '$department' GROUP by t.clientid

结果将以下列方式显示：

1   06:20:00    11:00:00                                            
2   06:20:00    11:00:00

在以下情况下查询：

DB::raw

我收到错误： SQLSTATE [21000]：基数违规：1242子查询返回超过1行

由于子查询返回多行。

在子查询中没有GROUP BY，结果如下：

orderBy

所以我的问题是如何构建查询以获得结果1.0

中显示的所需结果

非常欢迎任何帮助。谢谢！

Answer 1

无需使用子查询。您可以使用条件聚合：

SELECT SUM( CASE WHEN MONTH(`date`) = 2 THEN TIME_TO_SEC( `time` )  ELSE 0 END) AS February,
       SUM( CASE WHEN MONTH(`date`) = 12 THEN TIME_TO_SEC( `time` )  ELSE 0 END) AS December
FROM time_management
WHERE t.department = '$department'
GROUP BY clientid

这样您就可以计算一年中每个月的SUM time。

Answer 2

尝试使用：

SELECT SUM( CASE WHEN MONTH(`date`) = 2 THEN TIME_TO_SEC( `time` )  ELSE 0 END) AS February,
       SUM( CASE WHEN MONTH(`date`) = 12 THEN TIME_TO_SEC( `time` )  ELSE 0 END) AS December
FROM time_management
WHERE t.department = '$department'
GROUP BY clientid