Php 获取列和的SQL

我有三张桌子连在一起

mysql> select * from tablea;
+----+--------+
| id | name   |
+----+--------+
|  1 | Item 1 |
|  2 | Item 2 |
+----+--------+
2 rows in set (0.00 sec)

mysql> select * from tableb;
+----+------+----------+
| id | Aid  | name     |
+----+------+----------+
|  1 |    1 | B Item 1 |
|  2 |    2 | B Item 2 |
|  3 |    1 | B Item 3 |
+----+------+----------+
3 rows in set (0.00 sec)

mysql> select * from tablec;
+----+------+----------+-------+
| id | Bid  | name     | value |
+----+------+----------+-------+
|  1 |    1 | C Item 1 |    10 |
|  2 |    2 | C Item 2 |    20 |
|  3 |    1 | C Item 3 |    15 |
|  4 |    2 | C Item 4 |     5 |
|  5 |    3 | C Item 5 |    12 |
+----+------+----------+-------+
5 rows in set (0.00 sec)

表A通过Aid链接到表B，表C通过Bid链接到表B

我想要的是tableA的id，所有TableC项的值之和都在它下面

我期望上面示例的结果集是

+-----------+--------+
| tablea.id | sum    |
+-----------+--------+
|         1 |     37 |
|         2 |     25 |
+-----------+--------+

如果表a中的

ID

可能不存在于其他表中，并且您也希望显示其结果，请改用

LEFT JOIN

SELECT  a.ID, COALESCE(SUM(c.value), 0) totalValue
FROM    tablea a
        LEFT JOIN tableb b
            On a.ID = b.AID
        LEFT JOIN tablec c
            ON b.ID = c.BID
GROUP BY a.ID

您可以尝试此查询

SELECT a.id AS A, SUM(c.value) AS SUM FROM tablea a INNER JOIN tableb b ON a.id = b.Aid INNER JOIN tablec c ON b.id = c.Bid GROUP BY a.id;

---

你试过加入他们吗？

SELECT  a.ID, COALESCE(SUM(c.value), 0) totalValue
FROM    tablea a
        LEFT JOIN tableb b
            On a.ID = b.AID
        LEFT JOIN tablec c
            ON b.ID = c.BID
GROUP BY a.ID

SELECT a.id AS A, SUM(c.value) AS SUM FROM tablea a INNER JOIN tableb b ON a.id = b.Aid INNER JOIN tablec c ON b.id = c.Bid GROUP BY a.id;