想在MY SQL中的列组中使用行号吗？

Question

我在MYSQL中有一个表它有数据

Id Name 
1  test
1  test
1  test123
2  test222
3  test333

我想要像这样的数据

Id Name     RowNum
1  test       1
1  test       2
1  test123    1
2  test222    1
3  test333    1

意味着我想在Id和Name组上分配行号？

脚本应该怎么样？

Answer 1

这个表定义将实现你想要的.

CREATE TABLE  `test` (
  `Id` int(10) unsigned NOT NULL,
  `Name` varchar(45) NOT NULL,
  `RowNum` int(10) unsigned NOT NULL AUTO_INCREMENT,
  PRIMARY KEY (`Id`,`Name`,`RowNum`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1;

用数据填充表

INSERT INTO test VALUES
(1,"test",null),
(1,"test",null),
(1,"test123",null),
(2,"test222",null),
(3,"test333",null);

从表中选择数据

SELECT * FROM test;

结果

1, 'test', 1
1, 'test', 2
1, 'test123', 1
2, 'test222', 1
3, 'test333', 1

对于在查询中执行此操作,这是一种相当粗略的方法.

select g.id,g.name,g.rownum 
from (
    select t.id,t.name,
        @running:=if(@previous=concat(t.id,t.name),@running,0) + 1 as rownum,
        @previous:=concat(t.id,t.name) 
    from test t
    order by concat(t.id,t.name) 
) g;

Answer 2

这是另一种更简单的查询方式(至少对我而言):

SELECT
a.Id, a.Name,
(SELECT COUNT(*) FROM test
 WHERE Id = a.Id AND `Name` = a.Name AND row_id < a.row_id) AS RowNum
FROM test AS a
ORDER BY a.row_id;

这假设存在全局row_id(例如表中的自动增量主键).