PostgreSQL数据库执行mapper.xml时遇到结果映射（resultMap）关联的嵌套 Select 查询，多个参数传参入坑记

Posted 2021-05-15 Hi，all

目录

 

1.环境

2.mapper.xml 主查询，当前传参方式导致PostgreSQL数据库执行时，大写转小写

3.mapper.xml 主查询，保证传参时大写不改变

4.结果映射（resultMap）

5.关联的嵌套 Select 查询

6. 执行的SQL日志--主查询

7.执行的SQL日志-关联的嵌套 Select 查询

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1.环境

PostgreSQL数据库、SpringBoot 2.2.5.RELEASE、mybatis-plus 3.31

2.mapper.xml 主查询，当前传参方式导致PostgreSQL数据库执行时，大写转小写

因为：当前${type}传参方式，被认为是普通的字符串。PostgreSQL数据库会自动把大写转换为小写执行

<select id="getUsers" resultMap="getUsersMap">
    select u.*,cast(${type} as varchar) as orderType
    from
    sys_user u
</select>

3.mapper.xml 主查询，保证传参时大写不改变

<select id="getUsers" resultMap="getUsersMap">
    select u.*,cast(#{type} as varchar) as orderType
    from
    sys_user u
</select>

4.结果映射（resultMap）

<resultMap id="getUsersMap" type="com.xxx.SysUser">
        <id column="id" property="id"/>
        <result column="user_name" property="userName"/>
        <result column="state" property="state"/>
        <!--一对多-->
        <collection property="orders" select="queryOrders" javaType="list"
                    ofType="com.xxx.SysOrder" column="{id = id,orderType=orderType}">
            <id column="id" property="id"/>
            <result column="userId" property="userId"/>
            <result column="order_no" property="orderNo"/>
            <result column="order_state" property="orderState"/>
			<result column="order_type" property="orderType"/>
            <result column="address" property="address"/>
        </collection>
    </resultMap>

5.关联的嵌套 Select 查询

<select id="queryOrders" resultType="com.xxx.SysOrder">
        SELECT o.* from sys_order o
		<where>
			<if test="id != null ">
                AND o.user_id = #{id}
            </if>
			<if test="orderType != null and orderType != '' ">
                AND o.order_type = #{orderType}
            </if>
		</where>
    </select>

6. 执行的SQL日志--主查询

SELECT
	u.*, CAST ('PAY' AS VARCHAR) AS orderType
FROM
	sys_user u

7.执行的SQL日志-关联的嵌套 Select 查询

SELECT
	o.*
FROM
	sys_order o
WHERE
	o.user_id = 1
AND o.order_type = 'PAY'