连接几个表的SQL查询（MySQL）_Mysql_Sql_Select_Group By_Left Join

连接几个表的SQL查询（MySQL）

mysql sql select

连接几个表的SQL查询（MySQL）,mysql,sql,select,group-by,left-join,Mysql,Sql,Select,Group By,Left Join,我需要一个SQL查询（MySQL）的“小”帮助我有以下表格：快递员表格：交付表格：订单表格：坐标表格：在真实的数据库中，每个表中都有更多的列，但是对于这个示例，上面的列就足够了我需要什么一个SQL查询，返回所有信使[信使ID]，即他们的最后一个信使ID 交付[delivery\u ID]（基于上次的START\u日期）交货的上次坐标[LAT和LNG]（基于上次日期）和剩余订单计数（无完成日期的上次交货订单总数）快递员不能送货，在这种情况下，我想要送货\u ID= 空，LAT

我需要一个SQL查询（MySQL）的“小”帮助

我有以下表格：

快递员

表格：

交付

表格：

订单

表格：

坐标

表格：

在真实的数据库中，每个表中都有更多的列，但是对于这个示例，上面的列就足够了

我需要什么

一个SQL查询，返回所有信使[
```
信使ID
```
]，即他们的最后一个信使ID 交付[
```
delivery\u ID
```
]（基于上次的
```
START\u日期
```
）交货的上次坐标[
```
LAT
```
和
```
LNG
```
]（基于上次
```
日期
```
）和剩余订单计数（无
```
完成日期
```
的上次交货订单总数）
快递员不能送货，在这种情况下，我想要
```
送货\u ID
```
= 空，
```
LAT
```
=NULL和
```
LNG
```
=NULL
交付可以没有坐标，在这种情况下，我希望
```
LAT
```
=NULL 并且，
```
LNG
```
=结果中为空

我能做什么

SELECT c.`COURIER_ID`,
       d.`DELIVERY_ID`,
       r.`LAT`,
       r.`LNG`,
  (SELECT COUNT(DISTINCT `ORDER_ID`)
   FROM `ORDERS`
   WHERE `DELIVERY_ID` = d.`DELIVERY_ID`
     AND `FINISH_DATE` IS NULL) AS REMAINING_ORDERS

FROM `COURIERS` AS c
LEFT JOIN `DELIVERIES` AS d USING (`COURIER_ID`)
LEFT JOIN `COORDINATES` AS r ON r.`DELIVERY_ID` = d.`DELIVERY_ID`

WHERE (CASE WHEN
         (SELECT MAX(`START_DATE`)
          FROM `DELIVERIES`
          WHERE `COURIER_ID` = c.`COURIER_ID`) IS NULL THEN d.`START_DATE` IS NULL ELSE d.`START_DATE` =
         (SELECT MAX(`START_DATE`)
          FROM `DELIVERIES`
          WHERE `COURIER_ID` = c.`COURIER_ID`) END)
  AND (CASE WHEN
         (SELECT MAX(`DATE`)
          FROM `COORDINATES`
          WHERE `DELIVERY_ID` = d.`DELIVERY_ID`) IS NULL THEN r.`DATE` IS NULL ELSE r.`DATE` =
         (SELECT MAX(`DATE`)
          FROM `COORDINATES`
          WHERE `DELIVERY_ID` = d.`DELIVERY_ID`) END)
GROUP BY c.`COURIER_ID`
ORDER BY d.`START_DATE` DESC

问题是，当我有超过5k的

坐标时，这个查询非常慢（从5秒到20秒），有时它不会返回所有的快递员
非常感谢您提供的任何解决方案。
尝试以下方法：
SELECT C.COURIER_ID, D.DELIVERY_ID, D.START_DATE, D.FINISH_DATE, 
       B.LAT, B.LNG, B.DATE, C.NoOfOrders
FROM COURIERS C 
LEFT JOIN ( SELECT * 
            FROM (SELECT * 
                  FROM DELIVERIES D 
                  ORDER BY D.COURIER_ID, D.START_DATE DESC
                ) A 
            GROUP BY COURIER_ID
          ) AS A ON C.COURIER_ID = A.COURIER_ID 
LEFT JOIN ( SELECT * 
            FROM (SELECT * 
                  FROM COORDINATES CO 
                  ORDER BY CO.DELIVERY_ID, CO.DATE DESC
                ) B
            GROUP BY CO.DELIVERY_ID
          ) AS B ON A.DELIVERY_ID = B.DELIVERY_ID 
LEFT JOIN ( SELECT O.DELIVERY_ID, COUNT(1) NoOfOrders
            FROM ORDERS O WHERE FINISH_DATE IS NULL
            GROUP BY O.DELIVERY_ID
          ) AS C ON A.DELIVERY_ID = C.DELIVERY_ID;

我无法测试这个查询，因为我现在没有设置mysql数据库，更不用说这个模式和示例数据了。但我认为这会对你有用：
select
  c.courier_id
  , d.delivery_id
  , co.lat
  , co.lng
  , oc.cnt as remaining_orders
from
  couriers c
  left join (
    select
      d.delivery_id
      , d.courier_id
    from
      deliveries d
      inner join (
        select
          d.delivery_id
          , max(d.start_date) as start_date
        from
          deliveries d
        group by
          d.delivery_id
      ) dmax on dmax.delivery_id = d.delivery_id and dmax.start_date = d.start_date
  ) d on d.courier_id = c.courier_id
  left join (
    select
      c.delivery_id
      , c.lat
      , c.lng
    from
      coordinates c
      inner join (
        select
          c.delivery_id
          , max(c.date) as date
        from
          coordinates c
        group by
          c.delivery_id
      ) cmax on cmax.delivery_id = c.delivery_id and cmax.date = c.date
  ) co on co.delivery_id = d.delivery_id
  left join (
    select
      o.delivery_id
      , count(o.order_id) as cnt
    from
      orders o
    where
      o.finish_date is null
    group by
      o.delivery_id
  ) oc on oc.delivery_id = d.delivery_id

你真的没有问一个问题。看来您正在寻求帮助，以优化已编写的查询。你应该澄清你的问题。如果您正在寻求帮助以优化查询，则应该指定所需的结果。我认为这是一个问题，因为无论查询的性能如何，该查询都不能像我所需要的那样工作。性能只是问题之一。谢谢。您必须在单个数据库查询中返回所有结果吗？或者，只要最终结果是正确的数据集，您可以向数据库发出几个查询吗？如果您将示例数据与预期结果一起包含在表中，也会很有帮助。使用max（date）可能会得到多行，而不是最后一行。谢谢，我会试试你的答案，然后回来告诉你它是否有效。谢谢，我会试试你的答案，然后回来告诉你它是否有效。
    +-------------+-----+-----+------+
    | DELIVERY_ID | LAT | LNG | DATE |
    +-------------+-----+-----+------+

SELECT c.`COURIER_ID`,
       d.`DELIVERY_ID`,
       r.`LAT`,
       r.`LNG`,
  (SELECT COUNT(DISTINCT `ORDER_ID`)
   FROM `ORDERS`
   WHERE `DELIVERY_ID` = d.`DELIVERY_ID`
     AND `FINISH_DATE` IS NULL) AS REMAINING_ORDERS

FROM `COURIERS` AS c
LEFT JOIN `DELIVERIES` AS d USING (`COURIER_ID`)
LEFT JOIN `COORDINATES` AS r ON r.`DELIVERY_ID` = d.`DELIVERY_ID`

WHERE (CASE WHEN
         (SELECT MAX(`START_DATE`)
          FROM `DELIVERIES`
          WHERE `COURIER_ID` = c.`COURIER_ID`) IS NULL THEN d.`START_DATE` IS NULL ELSE d.`START_DATE` =
         (SELECT MAX(`START_DATE`)
          FROM `DELIVERIES`
          WHERE `COURIER_ID` = c.`COURIER_ID`) END)
  AND (CASE WHEN
         (SELECT MAX(`DATE`)
          FROM `COORDINATES`
          WHERE `DELIVERY_ID` = d.`DELIVERY_ID`) IS NULL THEN r.`DATE` IS NULL ELSE r.`DATE` =
         (SELECT MAX(`DATE`)
          FROM `COORDINATES`
          WHERE `DELIVERY_ID` = d.`DELIVERY_ID`) END)
GROUP BY c.`COURIER_ID`
ORDER BY d.`START_DATE` DESC

SELECT C.COURIER_ID, D.DELIVERY_ID, D.START_DATE, D.FINISH_DATE, 
       B.LAT, B.LNG, B.DATE, C.NoOfOrders
FROM COURIERS C 
LEFT JOIN ( SELECT * 
            FROM (SELECT * 
                  FROM DELIVERIES D 
                  ORDER BY D.COURIER_ID, D.START_DATE DESC
                ) A 
            GROUP BY COURIER_ID
          ) AS A ON C.COURIER_ID = A.COURIER_ID 
LEFT JOIN ( SELECT * 
            FROM (SELECT * 
                  FROM COORDINATES CO 
                  ORDER BY CO.DELIVERY_ID, CO.DATE DESC
                ) B
            GROUP BY CO.DELIVERY_ID
          ) AS B ON A.DELIVERY_ID = B.DELIVERY_ID 
LEFT JOIN ( SELECT O.DELIVERY_ID, COUNT(1) NoOfOrders
            FROM ORDERS O WHERE FINISH_DATE IS NULL
            GROUP BY O.DELIVERY_ID
          ) AS C ON A.DELIVERY_ID = C.DELIVERY_ID;

select
  c.courier_id
  , d.delivery_id
  , co.lat
  , co.lng
  , oc.cnt as remaining_orders
from
  couriers c
  left join (
    select
      d.delivery_id
      , d.courier_id
    from
      deliveries d
      inner join (
        select
          d.delivery_id
          , max(d.start_date) as start_date
        from
          deliveries d
        group by
          d.delivery_id
      ) dmax on dmax.delivery_id = d.delivery_id and dmax.start_date = d.start_date
  ) d on d.courier_id = c.courier_id
  left join (
    select
      c.delivery_id
      , c.lat
      , c.lng
    from
      coordinates c
      inner join (
        select
          c.delivery_id
          , max(c.date) as date
        from
          coordinates c
        group by
          c.delivery_id
      ) cmax on cmax.delivery_id = c.delivery_id and cmax.date = c.date
  ) co on co.delivery_id = d.delivery_id
  left join (
    select
      o.delivery_id
      , count(o.order_id) as cnt
    from
      orders o
    where
      o.finish_date is null
    group by
      o.delivery_id
  ) oc on oc.delivery_id = d.delivery_id