如何使用 laravel 查询生成器从表联合的结果中选择列？

Posted 2023-03-14

【中文标题】如何使用 laravel 查询生成器从表联合的结果中选择列？

【英文标题】：How do I select columns from results of union of tables using laravel query builder?

【发布时间】：2016-09-06 05:14:13

【问题描述】：

我正在尝试将我的 mysql 语句转换为 laravel 查询生成器。在以下查询中，我尝试对从三个表的 UNION-ing 结果中获取的列执行 GROUP BY 和 ORDER BY

staff_task_history_calibrate staff_task_history_samples staff_task_history_measures

你们有遇到过类似的吗？如果是的话，你能解释一下我的问题吗？

SELECT staff_name, task_id, task_type, task_desc, SUM(task_multiplier) 
FROM 
(
    (
    select CONCAT(S.first_name," ",S.last_name) as staff_name, 
    `STHC`.`task_id`, IFNULL(T.type, "-") as task_type, 
    `T`.`description` as `task_desc`, 
    STHC.task_multiplier
    from `staff_task_history_calibrate` as `STHC` 
    inner join `staffs` as `S` on `STHC`.`staff_id` = `S`.`staff_id` inner join `tasks` as `T` on `STHC`.`task_id` = `T`.`id` 
    ) 
    union 
    (
    select CONCAT(S.first_name," ",S.last_name) as staff_name, 
    `STHS`.`task_id`, IFNULL(T.type, "-") as task_type, 
    `T`.`description` as `task_desc`, 
    STHS.task_multiplier
    from `staff_task_history_samples` as `STHS` 
    inner join `staffs` as `S` on `STHS`.`staff_id` = `S`.`staff_id` inner join `tasks` as `T` on `STHS`.`task_id` = `T`.`id`
    ) 
    union 
    (
    select CONCAT(S.first_name," ",S.last_name) as staff_name, 
    `STHM`.`task_id`, IFNULL(T.type, "-") as task_type, 
    `T`.`description` as `task_desc`, 
    STHM.task_multiplier
    from `staff_task_history_measures` as `STHM` 
    inner join `staffs` as `S` on `STHM`.`staff_id` = `S`.`staff_id` inner join `tasks` as `T` on `STHM`.`task_id` = `T`.`id`
    )
) combined_tables
GROUP BY staff_name, task_type, task_desc
ORDER BY staff_name, task_type, task_desc;

【参考方案1】：

我很难测试，但请尝试：

// Build up the sub-queries
$sub1 = DB::table('staff_task_history_calibrate AS STHC')
          ->select(DB::raw(
            'CONCAT(S.first_name," ",S.last_name) as staff_name', 
            'STHC'.'task_id', 'IFNULL(T.type, "-") as task_type',
            'T'.'description' as 'task_desc', 'STHC.task_multiplier')
          )->join('staffs AS S', 'STHC.staff_id', '=', 'S.staff_id')
          ->join('tasks AS T', 'STHC.task_id', '=', 'T.id');

$sub2 = DB::table('staff_task_history_samples AS STHS')
          ->select(DB::raw(
            'CONCAT(S.first_name," ",S.last_name) as staff_name', 
            'STHS'.'task_id', 'IFNULL(T.type, "-") as task_type',
            'T'.'description' as 'task_desc', 'STHS.task_multiplier')
          )->join('staffs AS S', 'STHS.staff_id', '=', 'S.staff_id')
          ->join('tasks AS T', 'STHS.task_id', '=', 'T.id');

$sub3 = DB::table('staff_task_history_measures AS STHM')
          ->select(DB::raw(
            'CONCAT(S.first_name," ",S.last_name) as staff_name', 
            'STHM'.'task_id', 'IFNULL(T.type, "-") as task_type',
            'T'.'description' as 'task_desc', 'STHM.task_multiplier')
          )->join('staffs AS S', 'STHM.staff_id', '=', 'S.staff_id')
          ->join('tasks AS T', 'STHM.task_id', '=', 'T.id');


// Add the unions
$allUnions = $sub1->union($sub2)->union($sub3); // (Check the documentation for Unions in Query Builder)

// Get the results
$results = DB::table(DB::raw("($allUnions->toSql()) as combined_tables"))
       ->select('staff_name, task_id, task_type, task_desc')
       ->sum('task_multiplier')
       ->mergeBindings($allUnions) // We need to retrieve the underlying SQL
       ->groupBy('staff_name')
       ->groupBy('task_type')
       ->groupBy('task_desc')
       ->orderBy('staff_name')
       ->orderBy('task_type')
       ->orderBy('task_desc')
       ->get();

（如果你有什么工作，我会保留它。）

【讨论】：

我不明白使用mergeBindings 的原因。您能详细介绍一下这种方法吗？