将记录值合并到包含以逗号分隔的多个值的记录中

Question

我有这样的多对多表格架构，

|------------|          |--------------|            |-----------|
| Products   |-|-------<|ProductEngine |>---------|-|  Engines  |
|            |          |              |            |           |
|------------|          |--------------|            |-----------|

在内部联接查询之后，我在下面得到了一个结果集：

SELECT product_id, engine_id 
FROM Products 
INNER JOIN ProductEngine 
  ON Products.product_id=ProductEngine.product_id

+---------------+--------------+
| product_id    | engine_id    |
+---------------+--------------+
| P001          | E001         |
| P001          | E002         |
| P002          | E003         |
| P002          | E004         |
| P002          | E005         |
+---------------+--------------+

如果我想获得这样的结果，如何编写SQL查询？

+---------------+----------------+
| product_id    | engine_id      |
+---------------+----------------+
| P001          | E001,E002      |
| P002          | E003,E004,E005 |
+---------------+----------------+

Answer 1

他们是several techniques to converting row values into a string，我喜欢这个：

SELECT p1.product_id,
       substring(
          ( SELECT ',' + engine_id
              FROM ProductEngine p2
              WHERE p2.product_id = p1.product_id
              FOR XML PATH('') ), 2, 4000)
       AS engine_id
      FROM Products p1;

<强>被修改

现在正在按需要工作。 I have write an example to you