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过滤结果常用的是 where , limit
前者限制必须满足特定的结果, 后者 限制生产结果的个数
对于 limit 可以带一个参数n , 也可以带两个参数 m, n
前者表示 获得前n个结果
后者表示 从第m个开始的n个结果。 这里需要注意的是从0开始编号的。 也就是说第一结果的序号是0
示例:
创建一个表 插入数据
mysql> insert table tb_001 ( name , age) values ('name_1', 1), ('name_2', 2), ('name_3', 3), ('name_4', 4), ('name_5', 5); 1), ('name_2', 2), ('name_3', 3), (' at line 1 mysql> insert into tb_001 ( name , age) values ('name_1', 1), ('name_2', 2), ('name_3', 3), ('name_4', 4), ('name_5', 5); Query OK, 5 rows affected (0.08 sec) Records: 5 Duplicates: 0 Warnings: 0 mysql> insert into tb_001 ( name , age) values ('name_6', 6), ('name_7', 7), ('name_8', 8), ('name_9',9 ); Query OK, 4 rows affected (0.03 sec) Records: 4 Duplicates: 0 Warnings: 0
仅仅获得id小于等于2的数据
mysql> select * from tb_001 where (id <= 2 ); +----+--------+------+ | id | name | age | +----+--------+------+ | 1 | name_1 | 1 | | 2 | name_2 | 2 | +----+--------+------+ 2 rows in set (0.00 sec)
获得指定的个数
mysql> select * from tb_001 limit 2; +----+--------+------+ | id | name | age | +----+--------+------+ | 1 | name_1 | 1 | | 2 | name_2 | 2 | +----+--------+------+ 2 rows in set (0.00 sec) mysql> select * from tb_001 limit 2 ,3; +----+--------+------+ | id | name | age | +----+--------+------+ | 3 | name_3 | 3 | | 4 | name_4 | 4 | | 5 | name_5 | 5 | +----+--------+------+ 3 rows in set (0.02 sec)
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