mybatis中的转义字符

Mybatis转义字符表
<	<	小于
>	>	大于
&	&	与
'	'	单引号
"	"	双引号

需要注意的是分号是必不可少的。比如 a > b 我们就写成 a > b

二、常用的sql语句写法
1、模糊查询

user_name like CONCAT("%",#{userName},"%") and

2、月份查询

输入月份（2019-01），查找属于这个月份的记录

DATE_FORMAT(start_time,'%Y-%m') <![CDATA[ <= ]]> DATE_FORMAT(#{theMonth},'%Y-%m')
and
DATE_FORMAT(end_time,'%Y-%m') <![CDATA[ >= ]]>DATE_FORMAT( #{theMonth},'%Y-%m')
and

提示：DATE_FORMAT正则表达式(%Y-%m-%d %H:%i:%S)

3、时间区间查找

DATE_FORMAT(create_time,'%Y-%m-%d')  <![CDATA[ >= ]]> DATE_FORMAT(#{startTime},'%Y-%m-%d') 
and
DATE_FORMAT(create_time,'%Y-%m-%d')  <![CDATA[ <= ]]> DATE_FORMAT(#{endTime},'%Y-%m-%d') 
and

全部格式化成年月日格式进行时间对比。

4、resultMap嵌套

<resultMap id="UserInfoResultMap" type="com..entity.User">
        <id column="id" property="id" />
        <result column="user_name" property="userName" />
        <result column="password" property="password" />
        
        <collection ofType="com.entity.Image" property="imageList">
            <id column="image_id" property="id" />
            <result column="image_path" property="imagePath" />
            <result column="image_size" property="imageSize" />
        </collection>
    </resultMap>

collection 嵌套：
如user类中有一个image图片类的集合List imageList，要将每个人的图片都嵌套存放在各自的imageList属性中。

ofType：嵌套类的类名。这里就写图片类名称Image。
property：主类中属性名。这里就填user类中的imageList。
5、查询

<select id="selectUserList"
        parameterType="com.param.UserParam"
        resultMap="BaseResultMap">
        SELECT *
        FROM
        user
        <trim prefix="where"  suffixOverrides="and">
            <if test="userName != null">
                user_name LIKE CONCAT("%",#{userName},"%") and
            </if>
            
            <if test="startTime != null">
                DATE_FORMAT(create_time,'%Y-%m-%d')  <![CDATA[ >= ]]>  DATE_FORMAT(#{startTime},'%Y-%m-%d') 
                and
            </if>
            <if test="endTime != null">
                DATE_FORMAT(create_time,'%Y-%m-%d')  <![CDATA[ <= ]]> DATE_FORMAT(#{endTime},'%Y-%m-%d') 
                and
            </if>
            
            <trim prefix="id in(" suffix=")and" suffixOverrides=",">
                <foreach collection="idList" item="tiem">
                    #{tiem},
                </foreach>
            </trim>
            
        </trim>
    </select>

6、批量添加

<insert id="insertBatch"
        parameterType="com.entity.User"
        useGeneratedKeys="true" keyProperty="id">
        insert into
        user
        <trim prefix="(" suffix=")" suffixOverrides=",">
        
            name,
            age
            
        </trim>
        values
        <foreach collection="list" item="item" index="index"
            separator=",">
            <trim prefix="(" suffix=")" suffixOverrides=",">
            
                #{item.name},
                #{item.age},
                
            </trim>
        </foreach>
    </insert>

相当于insert into user （name,age）values (张，20),(李，21),(王，22)·····

7、批量更新

<update id="updateBatch"
        parameterType="com.safety.exam.entity.StaffAccount"
        useGeneratedKeys="true" keyProperty="id">
        update user  set 
        name =
        <foreach collection="list" item="item" index="index"
            open="case id" close="end">
            
            when #{item.id} then #{item.name}
            
        </foreach>,
        
        age =
        <foreach collection="list" item="item" index="index"
            open="case id" close="end">
            
            when #{item.id} then #{item.age}
            
        </foreach>
        
        where id in
        <foreach collection="list" index="index" item="item"
            separator="," open="(" close=")">
            #{item.id}
        </foreach>
        
    </update>

注意： set关键字只有一个；每个foreach之间有个逗号。
最后sql是这样：

UPDATE categories SET
        display_order = CASE id
            WHEN 1 THEN 3
            WHEN 2 THEN 4
            WHEN 3 THEN 5
        END,
        title = CASE id
            WHEN 1 THEN 'New Title 1'
            WHEN 2 THEN 'New Title 2'
            WHEN 3 THEN 'New Title 3'
        END
    WHERE id IN (1,2,3)