mybatis部分sql技巧

1、mybatis中没有<=号，必须用<![CDATA[<=]]>表示。<update id="reduceNumber">
        UPDATE
        seckill
        SET
        number = number - 1
        WHERE seckill_id =#{seckillId}
        AND start_time <![CDATA[<=]]>#{killTime}
        AND end_time >=#{killTime}
        AND number >0;
    </update>

2、mysql分页语句的写法

 <select id="queryAll" resultType="org.seckill.entity.Seckill">
        SELECT seckill_id,name,number,start_time,end_time,create_time
        FROM seckill
        ORDER BY create_time DESC
        limit #{offset},#{limit}
    </select>

3、主键冲突报错忽略添加ignore关键字

4、一对多联合查询，此处使用内联且Seckil为实体类名，不是表名字，进行映射。

<!--主键冲突，报错-->
    <insert id="insertSuccessKilled">
        INSERT ignore INTO success_killed(seckill_id,user_phone,state)
        VALUES (#{seckillId},#{userPhone},0)
    </insert>
    <!--根据id查询successKillId并携带seckill实体-->
    <select id="queryByIdWithSeckill" resultType="org.seckill.entity.SuccessKilled">
        SELECT
        sk.seckill_id,
        sk.user_phone,
        sk.state,
        sk.create_time,
        s.seckill_id "Seckill.seckill_id",
        s.name "Seckill.name",
        s.number "Seckill.number",
        s.start_time "Seckill.start_time",
        s.end_time "Seckill.end_time",
        s.create_time "Seckill.create_time"
        FROM success_killed sk INNER JOIN seckill s ON sk.seckill_id=s.seckill_id
        WHERE sk.seckill_id=#{seckillId} and sk.user_phone=#{userPhone}
    </select>

5、mybatis接口注解使用实例，加mapper注解

@Mapper
public interface OrderDao {

    @Select("select * from seckill_order where user_id=#{userId} and goods_id=#{goodsId}")
    public SecKillOrder getMiaoshaOrderByUserIdGoodsId(@Param("userId")long userId, @Param("goodsId")long goodsId);

    @Insert("insert into order_info(user_id, goods_id, goods_name, goods_count, goods_price, order_channel, status, create_date)values("
            + "#{userId}, #{goodsId}, #{goodsName}, #{goodsCount}, #{goodsPrice}, #{orderChannel},#{status},#{createDate} )")
    @SelectKey(keyColumn="id", keyProperty="id", resultType=long.class, before=false, statement="select last_insert_id()")//此处返回刚插入的主键id
    public long insert(OrderInfo orderInfo);

    @Insert("insert into seckill_order (user_id, goods_id, order_id)values(#{userId}, #{goodsId}, #{orderId})")
    public int insertMiaoshaOrder(SecKillOrder secKillOrder);
}