Mysql连接多个合计-提高查询效率

Question

我正在为员工创建一个签到/签退系统。

有一个tbl_clockins，它包含每个打卡/打卡会话的记录，其中包含关于每个会话是否支付工资、员工在该会话中迟到了多长时间或他们加班了多少等信息。

还有一个名为tbl_user_work_settings的表格，经理可以在其中设置员工放假或因病休假的日期。

我正在创建一些报告，其中我需要每个员工的总计，例如，每个员工在给定日期范围内休假的总天数。我有一个非常长的查询，它实际上获得了所有需要的信息，但它很大，效率有点低。有没有办法让它变得更小/更高效？任何帮助都是非常感谢的。

// get total days worked, unpaid days, bank holidays, holidays, sicknesses
// and absences within given date range for given users            
$sql = "SELECT us.username, daysWorked, secondsWorked,
            unpaidDays, bankHolidays, holidays, sicknesses, absences
FROM
  (SELECT username FROM users WHERE clockin_valid='1') us
  LEFT JOIN (
    SELECT   username, selectedDate, count(isUnpaid) AS unpaidDays
    FROM     tbl_user_work_settings
    WHERE    isUnpaid = '1'
         AND selectedDate>='$startDate'
         AND selectedDate<='$endDate'
    GROUP BY username
  ) u ON us.username=u.username
  LEFT JOIN (
    SELECT   username, count(isBankHoliday) AS bankHolidays
    FROM     tbl_user_work_settings
    WHERE    isBankHoliday='1'
         AND selectedDate>='$startDate'
         AND selectedDate<='$endDate'
    GROUP BY username
  ) bh ON us.username=bh.username
  LEFT JOIN (
    SELECT   username, count(isHoliday) AS holidays
    FROM     tbl_user_work_settings
    WHERE    isHoliday='1'
         AND selectedDate>='$startDate'
         AND selectedDate<='$endDate'
    GROUP BY username
  ) h ON us.username=h.username
  LEFT JOIN (
    SELECT   username, count(isSickness) AS sicknesses
    FROM     tbl_user_work_settings
    WHERE    isSickness='1'
         AND selectedDate>='$startDate'
         AND selectedDate<='$endDate'
    GROUP BY username
  ) s ON us.username=s.username
  LEFT JOIN (
    SELECT   username, count(isOtherAbsence) AS absences
    FROM     tbl_user_work_settings
    WHERE    isOtherAbsence='1'
         AND selectedDate>='$startDate'
         AND selectedDate<='$endDate'
    GROUP BY username
  ) a ON us.username=a.username
  LEFT JOIN (
    SELECT   username, count(DISTINCT DATE(in_time)) AS daysWorked,
                SUM(seconds_duration) AS secondsWorked
    FROM     tbl_clockins
    WHERE    DATE(in_time)>='$startDate'
         AND DATE(in_time)<='$endDate'
    GROUP BY username
  ) dw ON us.username=dw.username";

if(count($selectedUsers)>0)
  $sql .= " WHERE (us.username='"
       .  implode("' OR us.username='", $selectedUsers)."')";

$sql .= " ORDER BY us.username ASC";

Answer 1

您可以在tbl_user_work_settings表的一次使用中使用SUM(condition)：

// get total days worked, unpaid days, bank holidays, holidays, sicknesses
// and absences within given date range for given users            
$sql = "
  SELECT      users.username,
              SUM(ws.isUnpaid      ='1')       AS unpaidDays,
              SUM(ws.isBankHoliday ='1')       AS bankHolidays,
              SUM(ws.isHoliday     ='1')       AS holidays,
              SUM(ws.isSickness    ='1')       AS sicknesses,
              SUM(ws.isOtherAbsence='1')       AS absences,
              COUNT(DISTINCT DATE(cl.in_time)) AS daysWorked,
              SUM(cl.seconds_duration)         AS secondsWorked
  FROM        users
    LEFT JOIN tbl_user_work_settings           AS ws
           ON ws.username = users.username
          AND ws.selectedDate  BETWEEN '$startDate' AND '$endDate'
    LEFT JOIN tbl_clockins                     AS cl
           ON cl.username = users.username
          AND DATE(cl.in_time) BETWEEN '$startDate' AND '$endDate'
  WHERE       users.clockin_valid='1'";

if(count($selectedUsers)>0) $sql .= "
          AND users.username IN ('" . implode("','", $selectedUsers) . "')";

$sql .= "
  GROUP BY    users.username
  ORDER BY    users.username ASC";

顺便说一句(也许对其他读者更有好处)，我真的希望在将变量插入到之前，通过正确转义这些变量来避免SQL注入攻击。理想情况下，您根本不应该这样做，而应该将这样的变量作为预准备语句的参数传递给MySQL (不会对其进行计算)：阅读有关Bobby Tables的更多信息。

另外，为什么要将整数类型作为字符串来处理(通过用单引号将它们括起来)？在MySQL中执行不必要的类型转换是不必要的，也是对资源的浪费。实际上，如果不同的isUnpaid等列都是0/1，您可以更改上面的内容，删除相等性测试，直接使用SUM(ws.isUnpaid)等。

Answer 2

将每个要连接的表放入一个临时表中...然后在临时表的可接合字段上创建索引...并使用临时表进行查询。

示例：

SELECT   username, selectedDate, count(isUnpaid) AS unpaidDays
INTO     #TempTable1
FROM     tbl_user_work_settings
WHERE    isUnpaid = '1'
     AND selectedDate>='$startDate'
     AND selectedDate<='$endDate'
GROUP BY username
create clustered index ix1 on #TempTable1 (username)