mybatis sql 语句使用

MyBatis 是一款优秀的持久层框架，它支持定制化 SQL、存储过程以及高级映射。下面是 MyBatis 中常用的 SQL 语句使用示例：

1. 查询语句

单表查询：

<select id="selectUserById" resultType="com.example.User">
    select * from user where id = #{id}
</select>

多表查询：

<select id="selectUserAndOrderById" resultMap="userResultMap">
    select u.*, o.order_no, o.total_price
    from user u
    left join order o on u.id = o.user_id
    where u.id = #{id}
</select>

<resultMap id="userResultMap" type="com.example.User">
    <id property="id" column="id" />
    <result property="username" column="username" />
    <collection property="orders" ofType="com.example.Order">
        <result property="orderNo" column="order_no" />
        <result property="totalPrice" column="total_price" />
    </collection>
</resultMap>

2. 插入语句

<insert id="insertUser" parameterType="com.example.User">
    insert into user (id, username, password)
    values (#{id}, #{username}, #{password})
</insert>

3. 更新语句

<update id="updateUser" parameterType="com.example.User">
    update user set username = #{username}, password = #{password}
    where id = #{id}
</update>

4. 删除语句

<delete id="deleteUserById" parameterType="int">
    delete from user where id = #{id}
</delete>

以上只是 MyBatis 中 SQL 语句的示例，实际应用中可能需要更复杂的 SQL 语句，需要根据具体情况进行编写。