trim标签&&MyBatis内置参数

SQL标签：

可以处理拼接sql中 【开头】第一个and

可以处理拼接sql中 【开头或结尾】第一个and

开头：给拼接的sql加prefix="where" suffixOverrides="and"，处理拼接sql中开头第一个and

        select * from student1
        
            <if test="stuName != null and stuName != '' ">
                and stuName like  '%${stuName}%'
            if>
            <if test="graName != null and graName != '' ">
                and graName like  '%${graName}%'
            if>
            <if test="stuAge != null and stuAge != '' ">
                and stuAge like  '%${stuAge}%'
            if>
        
    

 

 结尾

        select * from student1
        
            <if test="stuName != null and stuName != '' ">
                stuName like  '%${stuName}%' and
            if>
            <if test="graName != null and graName != '' ">
                graName like  '%${graName}%' and
            if>
            <if test="stuAge != null and stuAge != '' ">
                stuAge =  #{stuAge} and
            if>
        
    

 

predix：拼接　　prefixOverrides：删除

 

内置参数:

　　_parameter：代表mybatis的输入参数

        /*select * from student1 where 1=1*/
        select * from student1
        
            
                stuName like  '%${_parameter.stuName}%' and
            if>
            <if test="graName != null and graName != '' ">
                graName like  '%${graName}%' and
            if>
            <if test="stuAge != null and stuAge != '' ">
                stuAge =  #{stuAge} and
            if>
        
    

　　_datebaseId：代表当前数据库的名字