使用通配符 (%%) 提高 MySQL 搜索性能?
mysqlmysqli database
不，只要您有前导通配符，MySQL 就不会提高搜索性能，因为 MySQL 将无法使用索引。如果您更改为 ‘anyLetter%’，那么它将能够使用索引
以下语法最好与尾随通配符一起使用。语法如下 −
SELECT *FROM yourTableName WHERE yoorColumnName LIKE ‘anyLetter%’;
创建表的查询如下 −
mysql> create table TrailingWildCardDemo -> ( -> Id int NOT NULL AUTO_INCREMENT, -> Name Varchar(20), -> PRIMARY KEY(Id) -> ); Query OK, 0 rows affected (0.71 sec)
现在，您可以使用 insert 命令在表中插入一些记录。查询如下 −
mysql> insert into TrailingWildCardDemo(Name) values('John');
Query OK, 1 row affected (0.13 sec)
mysql> insert into TrailingWildCardDemo(Name) values('Johnson');
Query OK, 1 row affected (0.17 sec)
mysql> insert into TrailingWildCardDemo(Name) values('Mike');
Query OK, 1 row affected (0.16 sec)
mysql> insert into TrailingWildCardDemo(Name) values('Kevin');
Query OK, 1 row affected (0.23 sec)
mysql> insert into TrailingWildCardDemo(Name) values('Adam');
Query OK, 1 row affected (0.20 sec)
mysql> insert into TrailingWildCardDemo(Name) values('Ethan');
Query OK, 1 row affected (0.16 sec)
mysql> insert into TrailingWildCardDemo(Name) values('James');
Query OK, 1 row affected (0.19 sec)
使用 select 语句显示表中的所有记录。查询如下 −
mysql> select *from TrailingWildCardDemo;
以下是输出 −
+----+---------+ | Id | Name | +----+---------+ | 1 | John | | 2 | Johnson | | 3 | Mike | | 4 | Kevin | | 5 | Adam | | 6 | Ethan | | 7 | James | +----+---------+ 7 rows in set (0.00 sec)
以下是尾随通配符的查询 −
mysql> select *from TrailingWildCardDemo where Name LIKE 'j%';
以下是输出 −
+----+---------+ | Id | Name | +----+---------+ | 1 | John | | 2 | Johnson | | 7 | James | +----+---------+ 3 rows in set (0.00 sec)
