mysql - 获取 MySQL 唯一键组合

Question

如果我创建了一个类似于以下内容的表：

CREATE TABLE MyTable(
    id1Part1 INT NOT NULL,
    id1Part2 INT NOT NULL,

    id2Part1 INT NOT NULL,
    id2Part2 INT NOT NULL,

    UNIQUE KEY (id1Part1, id1Part2),
    UNIQUE KEY (id2Part1, id2Part2)
);

我现在如何要求数据库给我两个“唯一键”元组？
（SHOW INDEX似乎没有这样做。）

Answer 1

我不确定你是否正在寻找这样的东西

select
constraint_name,
group_concat(column_name order by ordinal_position) as cols
from information_schema.key_column_usage
where table_schema = 'db_name' and table_name = 'table_name'
group by constraint_name

Answer 2

mysql 不能给你两个主键。看一下这个：

mysql> CREATE TABLE MyTable(
    ->     id1Part1 INT NOT NULL,
    ->     id1Part2 INT NOT NULL,
    -> 
    ->     id2Part1 INT NOT NULL,
    ->     id2Part2 INT NOT NULL,
    -> 
    ->     UNIQUE KEY (id1Part1, id1Part2),
    ->     UNIQUE KEY (id2Part1, id2Part2)
    -> );
Query OK, 0 rows affected (0.17 sec)

mysql> desc mytable;
+----------+---------+------+-----+---------+-------+
| Field    | Type    | Null | Key | Default | Extra |
+----------+---------+------+-----+---------+-------+
| id1Part1 | int(11) | NO   | PRI | NULL    |       |
| id1Part2 | int(11) | NO   | PRI | NULL    |       |
| id2Part1 | int(11) | NO   | MUL | NULL    |       |
| id2Part2 | int(11) | NO   |     | NULL    |       |
+----------+---------+------+-----+---------+-------+

它表明只有一个主键。