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我想获得一个所有我类标识码查询之后的PRODUCT_ID:如何进一步子查询从SQL查询中获取所有Product_ID?
SELECT * FROM tbl_Categories WHERE Class_ID = 1
-------------tbl_Categories------------------
| Category_ID | Class_ID | Product_ID |
| 1 | 1 | 2 |
| 2 | 1 | 3 |
| 3 | 4 | 4 |
| 1 | 1 | 1 |
应返回我1,2,3
我如何查询呢?