1. 動態查詢語句

• 可以根據傳入的bean來判斷，動態的拼接SQL語句

• SQL語句

    <select id="findUserInfo" parameterType="UserInfo" resultType="UserInfo">
        select * from userinfo
        <where>
            <if test="id!=0">
                and id = #{id}
            </if>
            <if test="name!=null and name!=''"
 
>
                and name like #{name}
            </if>
            <if test="address!=null and address!=''">
                and address like #{address}
            </if>
        </where>
    </select>

• Java語句

        SqlSession session = MyBatisUtil.openSession();
 

        UserInfoDao dao = session.getMapper(UserInfoDao.class);

        UserInfo u = new UserInfo();
        u.setId(4);
        u.setName("%a%");
        u.setAddress("%c%");

        session.commit();
        session.close();

此處的Like語句如果用#，需要在傳入的引數中設定%，如果用的是$，則需要在SQL語句中寫'%#{param}%'

• 使用#

    SQL：and
 
 name like #{name}
    Java：u.setName("%a%");

• 使用$

    SQL：name like '%${name}%'
    Java：u.setName("a");

2. 傳入多個引數

• 傳入多個引數時需要用集合或陣列進行傳值

• SQL

    <select id="findUserInfoByIdArray" resultType="UserInfo">
        select * from userinfo where id in
        <!-- item名稱沒有限制，和取值的屬性一致即可 -->
        <!--  collection為傳入的引數型別，可以為list或array，open為需要拼接的開始符號，separator為分割符號，close為結束符號 -->
        <foreach collection="array" item="id" open="(" separator="," close=")">
            #{id}
        </foreach>
    </select>

• Java

        SqlSession session = MyBatisUtil.openSession();
        UserInfoDao dao = session.getMapper(UserInfoDao.class);

        List<Integer> ids = new ArrayList<Integer>();
        ids.add(1);
        ids.add(2);
        ids.add(3);
        List<UserInfo> list = dao.findUserInfoByIds(ids);

        session.close();

3. SQL語句複用

• 被複用的SQL語句

<!-- SQL語句複用 -->
    <sql id="ids">
        where id in
        <foreach collection="list" item="id" open="(" separator="," close=")">
            #{id}
        </foreach>
    </sql>

• 使用

    <select id="findUserInfoByIds" resultType="UserInfo">
        select * from userinfo
        <!--refid為被複用的sql語句ID-->
        <include refid="ids" />
    </select>

4. 批量操作

• 使用foreach迴圈實現批量操作
• SQL

    <insert id="insertBatch" parameterType="java.util.List">
        insert into userinfo(id,name,address)
        values
        <foreach collection="list" item="data" separator=",">
            (#{data.id},#{data.name},#{data.address})
            </foreach>
    </insert>

• Java

        SqlSession session = MyBatisUtil.openSession();
        UserInfoDao dao = session.getMapper(UserInfoDao.class);

        List<UserInfo> list = new ArrayList<UserInfo>();

        UserInfo u1 = new UserInfo(5,"c5","dalian");
        UserInfo u2 = new UserInfo(6,"c6","dalian");
        UserInfo u3 = new UserInfo(7,"c7","dalian");
        UserInfo u4 = new UserInfo(8,"c8","dalian");
        UserInfo u5 = new UserInfo(9,"c9","dalian");

        list.add(u1);
        list.add(u2);
        list.add(u3);
        list.add(u4);
        list.add(u5);

        dao.insertBath(list);
        session.commit();
        session.close();

5. 動態的拼接更新語句

• 通過判斷條件來動態的拼接更新語句
• SQL

    <update id="updateUserInfo" parameterType="UserInfo">
        update userinfo
        <set>
            <if test="name!=null and name!=''">
                name=#{name},
            </if>
            <if test="address!=null and name!=''">
                address=#{address},
            </if>
        </set>
        where id=#{id}
    </update>

• Java

        SqlSession session = MyBatisUtil.openSession();
        UserInfoDao dao = session.getMapper(UserInfoDao.class);

        //此處不能所有值都為空，否則SQL語句沒有更新條件會有異常
        UserInfo u = new UserInfo(4, "啦啦啦", null);
        dao.updateUserInfo(u);

        session.commit();
        session.close();