Shulou(Shulou.com)06/01 Report--

The data of the character type does not use quotation marks, and the index will be suppressed. Here is an example:

View the table structure:

Click (here) to collapse or open

Mysql > show create table test06\ G

* * 1. Row *

Table: test06

Create Table: CREATE TABLE `test06` (

`id`bigint (11) NOT NULL DEFAULT'0'

`u_ id` bigint (11) NOT NULL

`openid` varchar (100) DEFAULT NULL

`unionid` varchar (100) DEFAULT NULL

`username` varchar (100) NOT NULL

`password` varchar (100) NOT NULL

`create_ time`datetime NOT NULL

KEY `idx_test03_ id` (`id`)

KEY `idx_test03_ name` (`username`)

KEY `idx_test06_crea_ time` (`create_ time`)

) ENGINE=InnoDB DEFAULT CHARSET=utf8

1 row in set (0.00 sec) username field without quotation marks:

Click (here) to collapse or open

Mysql > select * from test06 where username=13499770088

Empty set, 8208 warnings (5.77 sec)

Mysql > explain select * from test06 where username=13499770088

+-- +

| | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |

+-- +

| | 1 | SIMPLE | test06 | ALL | idx_test03_name | NULL | NULL | NULL | 2009559 | Using where |

+-+ username field in quotation marks:

Click (here) to collapse or open

Mysql > select * from test06 where username='13499770088'

Empty set (0.07 sec)

Mysql > explain select * from test06 where username='13499770088'

+-+-

| | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |

+-+-

| | 1 | SIMPLE | test06 | ref | idx_test03_name | idx_test03_name | 302 | const | 1 | Using index condition |

The query speed of +-+ is obviously faster. The execution plan is indexed, which is the normal way to write.

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