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  • Mybatis常用示例

    mybatis 增删改查示例:

    数据库和实体类映射  column:数据库字段值  property: 实体类对应值

    <resultMap id="BaseResultMap" type="com.user.api.entity.User">
            <id column="id" property="id"/>
            <result column="name" property="name"/>
            <result column="mobile" property="mobile"/>
            <result column="password" property="password"/>
            <result column="gender" property="gender"/>
            <result column="status" property="status"/>
        </resultMap>

     新增:新增之后返回新增数据ID

    <insert id="insert" parameterType="com.user.api.entity.User" useGeneratedKeys="true" keyProperty="id">
        insert into user (name, mobile, password, gender,status)
        values (#{name}, #{mobile},#{password}, #{gender},#{status})
     </insert>

    修改:

    <update id="updateUser" parameterType="com.user.api.entity.User" flushCache="true">
            update user
            <set>
                <if test="mobile != null and mobile != ''">mobile = #{mobile},</if>
                <if test="name != null and name != ''">name = #{name},</if>
                <if test="password != null and password != ''">password = #{password}</if>
            </set>
            where id = #{id}
        </update>

    删除:

    <delete id="delByChannelId">
        delete from user where id = #{id}
     </delete>

    查询:

    <sql id="where_sql">
            <where>
                <if test="id != null and id > 0">AND id = #{id}</if>
                <if test="name != null and name != ''">
                    <bind name="pattern" value="'%' + name + '%'"/>
                    AND name like #{pattern}
                </if>
                <if test="mobile != null and mobile != ''">AND mobile = #{mobile}</if>
            </where>
        </sql>
       <select id="listUsers" resultMap="BaseResultMap">
            SELECT * FROM user
            <include refid="where_sql"/>
            order by id desc limit #{limit},#{offset}
       </select>

    批量查询:

    <select id="listById" parameterType="java.util.List" resultMap="BaseResultMap">
            select * from user
            <where>
                <foreach collection="userIds" item="item" separator="OR">
                    id = #{item}
                </foreach>
            </where>
     </select>

    查询: choose when otherwise 一旦when条件成立 之后的when 则不会执行,条件都不满足则执行otherwise
    //当搜索条件输入了名字按照姓名查找,输入了手机号按手机号查找,否则查询name为张三的用户

    <select id="queryUser" resultType="com.user.api.entity.User">
        select * from tb_user WHERE sex=1
        <choose>
            <when test="name!=null and name.trim()!=''">
                and name like '%${name}%'
            </when>
            <when test="mobile!=null and mobile !=''">
                and mobile = #{mobile}
            </when>
            <otherwise>
                and name='张三'
            </otherwise>
        </choose>
      </select>

    查询: where if 判断条件如果成立则会执行对应内容

    <select id="getUser" resultType="com.user.api.entity.User">
        select * from user
        <where
        1=1
        <if test="name!=null and name.trim()!=''">
            and name like '%${name}%'
        </if>
        <if test="mobile!=null and mobile !=''">
            and mobile = #{mobile}
        </if>
        </where>
     </select>

    查询:left join, right join, join
    left join :左连接 会查询左表的所有数据 和满足on 条件的右表数据,没查询出的右表数据用空表示
    right join:右连接 会查询右表的所有数据 和满足on 条件的左表数据,没查询出的左表数据用空表示
    join: 即inner join 查询满足左右两表的交集数据

    对于单个字符的查询在进行if 判断时候需要写到双引号或者toString()
    <if test='gender!=null and gender == "1"'>
    and name like '%${name}%'
    </if>
    或者
    <if test="gender!=null and gender == '1'.toString()">
    and name like '%${name}%'
    </if>
    if条件判断number类型,没必要判断''的情况,只需判断null的情况
    <if test="status!=null">
    and status = #{status}
    </if>

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  • 原文地址:https://www.cnblogs.com/wlong-blog/p/15331013.html
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