sql - 返回具有来自另一个表的值的列的值

Question

我有以下 2 个示例表：

Orders: 
+--------+----------+
| UserID | ProductID| 
+--------+----------+
|      1 |    1     | 
|      2 |    4     |
|      3 |    3     | 
|      4 |    3     | 
+--------+----------+

Products:
+----------+-------+
| ProductID| Price | 
+----------+-------+
|      1   | A     | 
|      2   | D     | 
|      3   | G     |
|      4   | J     |
+----------+-------+

我想返回表ProductID中Products只有 value （或 has UserID）的Orders表。

所以结果将是下面的列：

+----------+
| ProductID| 
+----------+
|      1   |  
|      3   | 
|      4   |
+----------+

标签： sql

Answer 1

SELECT ProductID FROM Products WHERE ProductID IN (SELECT ProductID from Orders)