动态sql

where标签、if标签

<select id="selectCondition" resultType="Envs" parameterType="Envs">
     SELECT * FROM http_envs
   <where>
     <if test="id != null">
          id = #{id}
     </if>
     <if test="name != null">
          AND name = #{name}
     </if>
     <if test="desc != null">
          AND `desc` = #{desc}
     </if>
   </where>
</select>

判断数据对象Envs里id、name、desc不为空则动态添加sql语句

foreach标签

<select id="selectByIds" resultType="Envs" parameterType="list">
   SELECT * FROM http_envs
  <where>
     <foreach collection="list" open="id IN (" close=")" item="id" separator=",">
        #{id}
      </foreach>
  </where>
</select>

属性：

• collection：指定参数容器类型，（list-集合，array-数组）
• open：指定开始sql语句
• close：指定结束sql语句
• item：参数变量名
• separator：指定分隔符
•