Question

我有这张桌子：

self.delegate

我想按字母顺序排列`listId'的+----+--------+------+----------+ | id | listId | item | position | +----+--------+------+----------+ | 4 | 2 | z234 | 1 | | 5 | 2 | f324 | 2 | | 2 | 2 | gt22 | 3 | | 3 | 2 | aa11 | 4 | | 1 | 2 | b321 | 5 | +----+--------+------+----------+列。所以最后，它应该是这样的：

item

如果我需要在同一张桌子上运行+----+--------+------+----------+ | id | listId | item | position | +----+--------+------+----------+ | 3 | 2 | aa11 | 1 | | 1 | 2 | b321 | 2 | | 5 | 2 | f324 | 3 | | 2 | 2 | gt22 | 4 | | 4 | 2 | z234 | 5 | +----+--------+------+----------+按字母顺序排列项目，我该怎样UPDATE？

谢谢

PS：我这样做的原因是因为这些项目在一个表格中，可以向上或向下拖动到一个新位置，但我希望用户能够按字母顺序排序并重新执行如果他们愿意，请订购

Answer 1

这是一个解决方案：

SET @newPosition = 0;
SELECT id, listId, item, position, (@newPosition:=@newPosition + 1) AS newPosition 
FROM foo
ORDER BY item;

输出：

| id | listId | item | position | newPosition |
|----|--------|------|----------|-------------|
|  3 |      2 | aa11 |        4 |           1 |
|  1 |      2 | b321 |        5 |           2 |
|  5 |      2 | f324 |        2 |           3 |
|  2 |      2 | gt22 |        3 |           4 |
|  4 |      2 | Z234 |        1 |           5 |

小提琴：http://www.sqlfiddle.com/#!9/24f51/2/1

编辑：要进行更新，您可以执行以下操作：

SET @newPosition = 0;

UPDATE foo SET position = (
  SELECT tmp.newPosition FROM (
    SELECT id,listId,item,position,(@newPosition:=@newPosition + 1) AS newPosition 
    FROM foo
    ORDER BY item
  ) AS tmp WHERE tmp.id = foo.id
);

（sqlfiddle在这里有点破碎）完全小提琴：

SQL Fiddle

MySQL 5.6架构设置：

-- +----+--------+------+----------+
-- | id | listId | item | position |
-- +----+--------+------+----------+
-- |  4 |      2 | z234 |        1 |
-- |  5 |      2 | f324 |        2 |
-- |  2 |      2 | gt22 |        3 |
-- |  3 |      2 | aa11 |        4 |
-- |  1 |      2 | b321 |        5 |
-- +----+--------+------+----------+
CREATE TABLE foo (
  id INT,
  listId INT,
  item VARCHAR(5),
  position INT
);
INSERT INTO foo VALUES
(4, 2, 'Z234', 1),
(5, 2, 'f324', 2),
(2, 2, 'gt22', 3),
(3, 2, 'aa11', 4),
(1, 2, 'b321', 5);

SET @newPosition = 0;

UPDATE foo SET position = (
  SELECT tmp.newPosition FROM (
    SELECT id,listId,item,position,(@newPosition:=@newPosition + 1) AS newPosition 
    FROM foo
    ORDER BY item
  ) AS tmp WHERE tmp.id = foo.id
);

查询1 ：

SELECT * FROM foo

<强> Results ：

| id | listId | item | position |
|----|--------|------|----------|
|  4 |      2 | Z234 |        5 |
|  5 |      2 | f324 |        3 |
|  2 |      2 | gt22 |        4 |
|  3 |      2 | aa11 |        1 |
|  1 |      2 | b321 |        2 |

Answer 2

RC。刚刚用更新查询打败了我。主要的区别是我在一个查询中执行它而不是两个查询。我将用户变量设置在也可以工作的交叉连接中。

创建表/插入数据。

CREATE TABLE foo
    (`id` INT, `listId` INT, `item` VARCHAR(4), `position` INT)
;

INSERT INTO foo
    (`id`, `listId`, `item`, `position`)
VALUES
    (4, 2, 'z234', 1),
    (5, 2, 'f324', 2),
    (2, 2, 'gt22', 3),
    (3, 2, 'aa11', 4),
    (1, 2, 'b321', 5)
;

<强>查询

用您自己的表名替换foo ..

UPDATE 
 foo 
INNER JOIN (
  SELECT
     id
   , (@newPosition:=@newPosition + 1) AS newPosition 
FROM
 foo
ORDER BY
  item ASC
)
 AS foo_table
CROSS JOIN (
 SELECT @newPosition := 0
) AS init_user_var 
SET 
 foo.position =  foo_table.newPosition
WHERE
  foo.id = foo_table.id

<强>结果

1 queries executed, 1 success, 0 errors, 0 warnings

Query: UPDATE foo INNER JOIN ( SELECT id , (@newPosition:=@newPosition + 1) AS newPosition FROM foo ORDER BY item ASC ) as foo_table CR...

5 row(s) affected

<强>查询

SELECT * FROM foo ORDER BY position ASC

<强>结果

    id  listId  item    position  
------  ------  ------  ----------
     3       2  aa11             1
     1       2  b321             2
     5       2  f324             3
     2       2  gt22             4
     4       2  z234             5

根据ORDER更改列值

2 个答案: