choose语句
<select id="find" parameterType="map" resultType="User">
<!--name为空时,不加条件-->
select * from t_user
<if test="name!=null">
where
( username like #{name} or nickname like #{name})
</if>
<if test="sort!=null">
order by ${sort}
<choose>
<when test="order!=null"> ${order}</when>
<otherwise>asc</otherwise>
</choose>
</if>
limit #{pageOffset},#{pageSize}
</select>
<!-- 多个参数的形式,需要使用map来存储-->
<!-- 只要是#{}这种形式的,都会以?形式替代,对应字符串形式,都会加上引号-->
<!-- 只要是${}这种形式的,不会用?形式替代,传过来什么,就什么替代-->
<select id="find" parameterType="map" resultType="User">
<!--name为空时,不加条件-->
select * from t_user
<if test="name!=null">
where
( username like #{name} or nickname like #{name})
</if>
order by ${sort} ${order}
limit #{pageOffset},#{pageSize}
</select>
<select id="count" parameterType="map" resultType="int">
select count(*) from t_user
<if test="name!=null">
where
( username like #{name} or nickname like #{name})
</if>
</select>
where语句
<select id="find" parameterType="map" resultType="User">
select * from t_user
<where>
<if test="name!=null">
<!--第一个条件不加and,后面几个都加-->
( username like #{name} or nickname like #{name})
</if>
<if test="type!=null">
and type=#{type}
</if>
</where>
limit #{pageOffset},#{pageSize}
<!--
对应的sql便是
select * from t_user where (username like ? or nickname like ?)
order by id desc limit ? ?
-->
</select>