一、mybatis if 條件判斷為空處理

<if test="userId != null and userId != '' ">

? ? and u.userId = #{userId}

</if>

二、mybatis if 條件對比字符串是否相等

<if test="userId != null and userId != '' ">

? ? <if test='userId == "0" '>

? ??????and u.userId = #{userId}

????</if>

</if>

注：?<if test='userId == "0" '>? 值必須用 " " ，外層必須是 ' '

三、mybatis if條件判斷寫法

<choose>

? ? <when test="userId != null and userId != '' ">

????????and u.userId = #{userId}

????</when>

? ? <otherwise>

? ??????and u.userId like #{userId}||'%'

????</otherwise>

</choose>