使用mybatis完成增删改查

插入

插入数据

<insert id="insertUser2" parameterType="UserEntity">
   insert into user values(null,#{userName},#{passWord} ,#{age})
</insert>

批量插入

<insert id="insertForeach" parameterType="java.util.List" >
    insert into user values 
    <foreach item="item" index="index" collection="list"  separator="," >
        (#{item.id},#{item.userName},#{item.passWord},#{item.age})
    </foreach>
</insert>

删除

删除数据

<delete id="delUser" parameterType="int">
    DELETE from user where id = #{id};
</delete>

批量删除

<delete id="deleteForeach" parameterType="java.util.List">
    delete from user where id in
    <foreach item="item" collection="list" open="(" separator="," close=")">#{item}</foreach>
</delete>

更新

更新数据

<update id="updateUser" parameterType="UserEntity">
    UPDATE user set username = #{userName},password=#{passWord} where id = #{id}
</update>

//选择局部更新
<update id="updateSet" parameterType="UserEntity" >
　　update user 
　　<set>
　　　　<if test="userName!=null">username=#{userName},</if>
　　　　<if test="passWord!=null">password=#{passWord}</if>
　　</set>
　　where id=#{id}
</update>

批量更新

<update id="updateForeach" parameterType="java.util.List">
        <foreach collection="list" item = "item" separator=";">
            update user
        <set>
            <if test="item.userName !=null">username=#{item.userName},</if>
            <if test="item.passWord !=null">password=#{item.passWord}</if>
        </set>
        where id=#{item.id}
        </foreach>
</update>

查询

查询全部,模糊查询,相应变量查询

<select id="selectAll" resultType="com.cc.bean.UserEntity">
    select <include refid="userSqlAll"></include> from user
</select>

<select id="selectLike"  parameterType="string" resultType="com.cc.bean.UserEntity">
    select <include refid="userSqlAll"></include> from user where username like concat("%",#{string},"%");
</select>


<update id="updateUser" parameterType="UserEntity">
        UPDATE user set username = #{userName},password=#{passWord} where id = #{id}
</update>

可变变量查询

<select id="selectWhere" parameterType="UserEntity" resultMap="mapUser">
        select <include refid="userSqlAll"></include> from user
        <where>
            <if test="id>0">and id = #{id}</if>
            <if test="userName1=null">and username=#{userName}</if>
            <if test="passWord!=null">and password=#{passWord}</if>
        </where>
        
</select>

<select id="selectTrim" parameterType="UserEntity" resultMap="mapUser">
        select <include refid="userSqlAll"></include> from user
        <trim prefix="where" prefixOverrides="and|or">
            <if test="id>0">and id = #{id}</if>
            <if test="userName1=null">and username=#{userName}</if>
            <if test="passWord!=null">and password=#{passWord}</if>
        </trim>
</select>

<select id="selectIf" parameterType="UserEntity" resultMap="mapUser">
        select <include refid="userSqlAll"></include> from user where 1 = 1
        <if test="userName!=null">and username=#{userName}</if>
        <if test="passWord!=null">and password=#{passWord}</if>
</select>

<select id="selectChoose" parameterType="UserEntity" resultMap="mapUser">
        select <include refid="userSqlAll"></include> from user where 1 = 1
        <choose>
            <when test="userName!=null">and username=#{userName}</when>
            <when test="passWord!=null">and password=#{passWord}</when>
            <otherwise>and 1 = 1</otherwise>
        </choose>
</select>

批量查询

<select id="selectForeachIn" parameterType="java.util.List" resultMap="mapUser">
        select <include refid="userSqlAll"></include> from user where id in
        <foreach item="item" collection="list" open="(" separator="," close=")">#{item}</foreach>
</select>

注意事项

resultMap进行实体类和数据库表名映射
<resultMap type="UserEntity" id="mapUser">
        <id property="id" column="id"></id>
        <!-- 非主键 -->
        <result property="userName" column="username"></result>
        <result property="passWord" column="password"></result>
        <result property="age" column="age"></result>
</resultMap>

sql标签和include标签简写sql
<sql id="userSqlAll">id,username,password,age</sql>
<include refid="userSqlAll"></include>

每一个标签的id值对应一个dao层的接口方法