根据另一个查询的排序顺序更新列

Question

我正在尝试将任意排序的记录添加到数据库中，以便它们可以通过 ui 进行排序（或者当我查询数据库时）。我的问题是我已经有了这个列表，我需要添加一个基于字母顺序的默认排序。我想我应该能够通过子查询或合并来做到这一点，但我无法正确地做到这一点。我在 MySQL 上执行此操作，因此我希望可以在数据库级别执行此操作。

Answer 1

先从一张表开始，把数据放进去，添加一个排序顺序列

USE test
DROP TABLE IF EXISTS ordered_names;
CREATE TABLE ordered_names
(
    id int not null auto_increment,
    firstname VARCHAR(20),
    lastname VARCHAR(20),
    PRIMARY KEY (id),
    KEY name_ndx (lastname,firstname)
);
INSERT INTO ordered_names (firstname,lastname) VALUES
('pamela','edwards'),('rolando','edwards'),('diamond','edwards');
ALTER TABLE ordered_names ADD COLUMN sort_order INT DEFAULT NULL;
SELECT * FROM ordered_names;

让我们实际运行一下：

mysql> USE test
Database changed
mysql> DROP TABLE IF EXISTS ordered_names;
Query OK, 0 rows affected (0.00 sec)

mysql> CREATE TABLE ordered_names
    -> (
    ->     id int not null auto_increment,
    ->     firstname VARCHAR(20),
    ->     lastname VARCHAR(20),
    ->     PRIMARY KEY (id),
    ->     KEY name_ndx (lastname,firstname)
    -> );
Query OK, 0 rows affected (0.04 sec)

mysql> INSERT INTO ordered_names (firstname,lastname) VALUES
    -> ('pamela','edwards'),('rolando','edwards'),('diamond','edwards');
Query OK, 3 rows affected (0.00 sec)
Records: 3  Duplicates: 0  Warnings: 0

mysql> ALTER TABLE ordered_names ADD COLUMN sort_order INT DEFAULT NULL;
Query OK, 3 rows affected (0.17 sec)
Records: 3  Duplicates: 0  Warnings: 0

mysql> SELECT * FROM ordered_names;
+----+-----------+----------+------------+
| id | firstname | lastname | sort_order |
+----+-----------+----------+------------+
|  1 | pamela    | edwards  |       NULL |
|  2 | rolando   | edwards  |       NULL |
|  3 | diamond   | edwards  |       NULL |
+----+-----------+----------+------------+
3 rows in set (0.00 sec)

mysql>

接下来，让我们填充排序顺序列：

SET @x = 0;
UPDATE ordered_names SET sort_order = (@x:=@x+1) ORDER BY lastname,firstname;
SELECT * FROM ordered_names;

让我们运行：

mysql> SET @x = 0;
Query OK, 0 rows affected (0.00 sec)

mysql> UPDATE ordered_names SET sort_order = (@x:=@x+1) ORDER BY lastname,firstname;
Query OK, 3 rows affected (0.00 sec)
Rows matched: 3  Changed: 3  Warnings: 0

mysql> SELECT * FROM ordered_names;
+----+-----------+----------+------------+
| id | firstname | lastname | sort_order |
+----+-----------+----------+------------+
|  1 | pamela    | edwards  |          2 |
|  2 | rolando   | edwards  |          3 |
|  3 | diamond   | edwards  |          1 |
+----+-----------+----------+------------+
3 rows in set (0.00 sec)

mysql>

好的，到目前为止很好，让我们再添加四 (4) 个人并重新排序：

INSERT INTO ordered_names (firstname,lastname) VALUES
('javonne','washington'),('richard','washington'),
('carlik','washington'),('dominique','edwards');
SET @x = 0;
UPDATE ordered_names SET sort_order = (@x:=@x+1) ORDER BY lastname,firstname;
SELECT * FROM ordered_names;

让我们运行：

mysql> INSERT INTO ordered_names (firstname,lastname) VALUES
    -> ('javonne','washington'),('richard','washington'),
    -> ('carlik','washington'),('dominique','edwards');
Query OK, 4 rows affected (0.00 sec)
Records: 4  Duplicates: 0  Warnings: 0

mysql> SET @x = 0;
Query OK, 0 rows affected (0.00 sec)

mysql> UPDATE ordered_names SET sort_order = (@x:=@x+1) ORDER BY lastname,firstname;
Query OK, 6 rows affected (0.00 sec)
Rows matched: 7  Changed: 6  Warnings: 0

mysql> SELECT * FROM ordered_names;
+----+-----------+------------+------------+
| id | firstname | lastname   | sort_order |
+----+-----------+------------+------------+
|  1 | pamela    | edwards    |          3 |
|  2 | rolando   | edwards    |          4 |
|  3 | diamond   | edwards    |          1 |
|  4 | javonne   | washington |          6 |
|  5 | richard   | washington |          7 |
|  6 | carlik    | washington |          5 |
|  7 | dominique | edwards    |          2 |
+----+-----------+------------+------------+
7 rows in set (0.00 sec)

mysql>

试一试 ！！！