Mysql的模糊查询

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1.数据库查询：select * from user_role

where ROLE_NAME LIKE '_i%'

2.concat函数理解：

SQL CONCAT函数用于将两个字符串连接起来，形成一个单一的字符串。试试下面的例子：

SQL> SELECT CONCAT('FIRST ', 'SECOND');+----------------------------+| CONCAT('FIRST ', 'SECOND') |+----------------------------+| FIRST SECOND               |+----------------------------+1 row in set (0.00 sec)

想要更详细了解CONCAT函数，考虑EMPLOYEE_TBL的表具有以下记录：

SQL> SELECT * FROM employee_tbl;+------+------+------------+--------------------+| id   | name | work_date  | daily_typing_pages |+------+------+------------+--------------------+|    1 | John | 2007-01-24 |                250 ||    2 | Ram  | 2007-05-27 |                220 ||    3 | Jack | 2007-05-06 |                170 ||    3 | Jack | 2007-04-06 |                100 ||    4 | Jill | 2007-04-06 |                220 ||    5 | Zara | 2007-06-06 |                300 ||    5 | Zara | 2007-02-06 |                350 |+------+------+------------+--------------------+7 rows in set (0.00 sec)

现在，假设根据上述表要连接名员工ID和work_date，那么你可以使用下面的命令：

SQL> SELECT CONCAT(id, name, work_date)    -> FROM employee_tbl;+-----------------------------+| CONCAT(id, name, work_date) |+-----------------------------+| 1John2007-01-24             || 2Ram2007-05-27              || 3Jack2007-05-06             || 3Jack2007-04-06             || 4Jill2007-04-06             || 5Zara2007-06-06             || 5Zara2007-02-06             |+-----------------------------+7 rows in set (0.00 sec)

3.<select id="queryList" resultMap="PlatFormResultMap">
       select * from PLATFORM
       where 1=1
       <if test="name !=null and name !=''">
           and name like CONCAT('%',#{name},'%' )
       </if>
       <if test="limit != null and limit!='' and limit != 0">
           limit #{start},#{limit}
       </if>
   </select>

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