将两个表转换为单个表

Question

我有这两个表：

+-------------+--------+      +----+-------+
| employee_id | val_id |      | id | value |
+-------------+--------+      +----+-------+
|         123 |      1 |      |  1 |     A |
+-------------+--------+      +----+-------+
|         123 |      2 |      |  2 |     B |
+-------------+--------+      +----+-------+
|         123 |      3 |      |  3 |     C |
+-------------+--------+      +----+-------+

预期结果

+-------------+-------+-------+-------+ 
| employee_id | val_1 | val_2 | val_3 | ...
+-------------+-------+-------+-------+ 
|         123 |     A |     B |     C |

请你帮帮我

Answer 1

1. 在第一个表中创建值列
2. 按更新子句更新'value'列（您可以使用subselect选择值）
3. DROP val_id列
4. DROP第二张表
桌子有多大？

Answer 2

使用join和pivot。这将提供所需的结果

SELECT * FROM(
SELECT employeeID,'val_'+CAST(a.val_id AS VARCHAR(2)) val_id ,value 
FROM table1 a INNER JOIN table2 b ON a.val_id=b.val_id
) AS ss
PIVOT
(
    MAX(value)
    FOR [val_id] IN ([val_1],[val_2],[val_3])
)AS pivott