我们的项目中有好多不等于的情况。今天写这篇文章简单的分析一下怎么个优化法。
这里的分表逻辑是根据t_group表的user_name组的个数来分的。
因为这种情况单独user_name字段上的索引就属于烂索引。起不了啥名明显的效果。

1、试验PROCEDURE.
DELIMITER $$
DROP PROCEDURE `t_girl`.`sp_split_table`$$
CREATE PROCEDURE `t_girl`.`sp_split_table`()
BEGIN
declare done int default 0;
declare v_user_name varchar(20) default ;
declare v_table_name varchar(64) default ;
-- Get all users name.
declare cur1 cursor for select user_name from t_group group by user_name;
-- Deal with error or warnings.
declare continue handler for 1329 set done = 1;
-- Open cursor.
open cur1;
while done <> 1
do
fetch cur1 into v_user_name;
if not done then
-- Get table name.
set v_table_name = concat(t_group_,v_user_name);
-- Create new extra table.
set @stmt = concat(create table ,v_table_name, like t_group);
prepare s1 from @stmt;
execute s1;
drop prepare s1;
-- Load data into it.
set @stmt = concat(insert into ,v_table_name, select * from t_group where user_name = ,v_user_name,);
prepare s1 from @stmt;
execute s1;
drop prepare s1;
end if;
end while;
-- Close cursor.
close cur1;
-- Free variable from memory.
set @stmt = NULL;
END$$

DELIMITER ;

2、试验表。
我们用一个有一千万条记录的表来做测试。

mysql> select count(*) from t_group;
+----------+
| count(*) |
+----------+
| 10388608 |
+----------+
1 row in set (0.00 sec)

表结构。
mysql> desc t_group;
+-------------+------------------+------+-----+-------------------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------------+------------------+------+-----+-------------------+----------------+
| id | int(10) unsigned | NO | PRI | NULL | auto_increment |
| money | decimal(10,2) | NO | | | |
| user_name | varchar(20) | NO | MUL | | |
| create_time | timestamp | NO | | CURRENT_TIMESTAMP | |
+-------------+------------------+------+-----+-------------------+----------------+
4 rows in set (0.00 sec)

索引情况。

mysql> show index from t_group;
+---------+------------+------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+
|Table | Non_unique | Key_name | Seq_in_index | Column_name |Collation | Cardinality | Sub_part | Packed | Null | Index_type |Comment |
+---------+------------+------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+
|t_group | 0 | PRIMARY | 1 | id |A | 10388608 | NULL | NULL | | BTREE | |
| t_group | 1 | idx_user_name | 1 | user_name | A | 8 | NULL | NULL | |BTREE | |
| t_group | 1 | idx_combination1| 1 | user_name | A | 8 | NULL |NULL | | BTREE | |
| t_group | 1 |idx_combination1 | 2 | money | A | 3776| NULL | NULL | | BTREE | |
+---------+------------+------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+
4 rows in set (0.00 sec)