用逗号分隔的列表从联接更新数据库表字段
我有两个名为 Districts 和 Schools 的表.Districts 表包含一个名为 Schools 的列.
I have two tables named Districts and Schools. The Districts table contains a column named Schools.
我需要从对应的 Schools 表中填充 Districts 表的 Schools 列，以便 中的每一行Districts 表有一个逗号分隔的Schools 表中的学校名称值列表.
I need to populate the Schools column of the Districts table from the corresponding Schools table, so that each row in the Districts table has a comma separated list of values of school names from the Schools table.
我该怎么做?我应该使用 UPDATE 查询还是存储过程?
How can I do this? Should I use an UPDATE query or a stored procedure?
我只知道:
SQL 小提琴
地区表
+------------+------+---------+
| DistrictId | Name | Schools |
+------------+------+---------+
| 1 | a | |
| 2 | b | |
| 3 | c | |
| 4 | d | |
+------------+------+---------+
学校表
+----------+------------+------------+
| SchoolId | SchoolName | DistrictId |
+----------+------------+------------+
| 1 | s1 | 1 |
| 2 | s2 | 1 |
| 3 | s3 | 2 |
| 4 | s4 | 2 |
| 5 | s5 | 4 |
+----------+------------+------------+
输出需要如何
+------------+------+---------+
| DistrictId | Name | Schools |
+------------+------+---------+
| 1 | a | s1,s2 |
| 2 | b | s3,s4 |
| 3 | c | |
| 4 | d | s5 |
+------------+------+---------+
推荐答案
借助 FOR XML PATH 和 STUFF 来连接这些值，您可以轻松地用您想要的结果更新表 District.
UPDATE a
SET a.Schools = b.SchoolList
FROM Districts a
INNER JOIN
(
SELECT DistrictId,
STUFF((SELECT ', ' + SchoolName
FROM Schools
WHERE DistrictId = a.DistrictId
FOR XML PATH (''))
, 1, 1, '') AS SchoolList
FROM Districts AS a
GROUP BY DistrictId
) b ON A.DistrictId = b.DistrictId
WHERE b.SchoolList IS NOT NULL
- SQLFiddle 演示
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