动态SQL做增删改查操作

1.什么是动态SQL

sql的内容是变化的, 可以根据条件获取到不同的sql语句.
主要是where部分发生变化。
动态sql的实现, 使用的是mybatis提供的标签

2.动态SQL常用标签

元素	作用	描述
if	条件判断	单条件判断
choose(when、otherwise)	条件选择	多条件分支判断
where.set	辅助(条件)	处理SQL语句拼接问题
foreach	循环(批量插入 修改)	循环遍历

3.具体使用

mapper.xml文件

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="ShopInfoMapper">
    <sql id="tableName" >
        `shop_info`
    </sql>
    <sql id="columns">
        `shop_info_name`,
		`shop_info_price`,
		`shop_info_remark`,
        `modify_time`
    </sql>
    <sql id="params">
        #{shop_info_name},
        #{shop_info_price},
        #{shop_info_remark},
        #{modify_time}
    </sql>
    <sql id="primaryKey">
        `shop_info_id`
    </sql>
    <sql id="id">
        ${zyu.id}
    </sql>

    <!-- 动态查询语句 -->
    <select id="query" resultType="map" parameterType="map">
        select
        <include refid="primaryKey"></include>,<include refid="columns"></include>
        from
        <include refid="tableName"></include>
        <trim prefix="where" prefixOverrides="and |or" >
            <if test="map!=null">
                <foreach collection="map"  index ="key"  item="val" separator=" and ">
                    ${key} = #{val}
                </foreach>
            </if>
        </trim>
        where
        <![CDATA[ del=1 ]]>
    </select>
    <!-- 动态查询列表总数语句 -->
    <select id="queryCount" resultType="map" parameterType="map">
        select
        count(*) `count`
        from
        <include refid="tableName"></include>
        <trim prefix="where" prefixOverrides="and |or" >
            <if test="map!=null">
                <foreach collection="map"  index ="key"  item="val" separator=" and ">
                    ${key} = #{val}
                </foreach>
            </if>
        </trim>
    </select>

    <!-- 动态修改语句 -->
    <update id="update"  parameterType="map">
        update
        <include refid="tableName"></include>
        <set>
            <foreach collection="zyu"  index ="key"  item="val" separator=",">
            <if test="key !='id'">
                ${key} = #{val}
            </if>
            </foreach>
        </set>
        <where>
            <include refid="primaryKey"></include> = <include refid="id"></include>
        </where>
    </update>


    <!-- 动态新增语句 -->
    <insert id="add" parameterType="map">
        <selectKey resultType="INTEGER" order="AFTER" keyProperty="shop_info_id">
            SELECT LAST_INSERT_ID()
        </selectKey>
        insert into
        <include refid="tableName"></include>
        (
        <include refid="columns"></include>
        )
        values
        (
        <include refid="params"></include>
        )
    </insert>

    <!-- 逻辑删除语句 -->
    <update id="del"  parameterType="map">
        update
        <include refid="tableName"></include>
        set
        <![CDATA[ del=0 ]]>

        where
        shop_info_id in (${id})
    </update>
</mapper>

具体使用可自己自行修改参数