sql - 使用取决于列值的值连接表

Question

我有 1 张长桌和 1 张短桌：

长桌是这样的：

LongTable:

+--------------+----------+----------+----------+
| Kabelnummer  |     GL   |more data |even more |           
+--------------+----------+----------+----------+
| 1            |    850   |    x     |    x     |
+--------------+----------+----------+----------+
| 2            |    850   |    x     |    x     |
+--------------+----------+----------+----------+
| 3            |   1300   |    x     |    x     |
+--------------+----------+----------+----------+
| 4            |   1300   |    x     |    x     |
+--------------+----------+----------+----------+

和

ShortTable:

+--------------+----------+----------+----------+
| data         |     GL   |more data |numericVal|           
+--------------+----------+----------+----------+
|      x       |    850   |    x     | 0.2345   |
+--------------+----------+----------+----------+
|      x       |   1300   |    x     | 0.2849   |
+--------------+----------+----------+----------+

我想要一个将列“numericVal”复制到表“LongTable”中的查询，其中 GL.Longtable 与 GL.shorttable 相同：

LongTable:

+--------------+----------+----------+----------+----------+
| Kabelnummer  |     GL   |more data |even more |numericVal|          
+--------------+----------+----------+----------+----------+
| 1            |    850   |    x     |    x     | 0.2345   |
+--------------+----------+----------+----------+----------+
| 2            |    850   |    x     |    x     | 0.2345   |
+--------------+----------+----------+----------+----------+
| 3            |   1300   |    x     |    x     | 0.2849   |
+--------------+----------+----------+----------+----------+
| 4            |   1300   |    x     |    x     | 0.2849   |
+--------------+----------+----------+----------+----------+

我该怎么做呢？

Answer 1

尝试将两个表加入INNER JOIN：

SELECT L.*, s.numericVal 
  FROM LongTable l 
  JOIN sortTable s
    ON l.GL = s.GL

Answer 2

SELECT lt.Kabelnummer, lt.GL, lt.X, lt.Y, st.numericVal
FROM LongTable lt
INNER JOIN ShortTable st ON lt.GL = st.GL

您使用 aJOIN来完成此操作。

您可以在此处阅读有关联接的信息：

加入基础