MyBatis--动态sql

数据库文件在http://www.cnblogs.com/wtzl/p/8758624.html

1.if---条件成立则拼接sql语句

<!-- if -->
    <select id="getUserListByUser" resultType="Person" parameterType="Person">
        select * from smbms_user 
            where userName like CONCAT ('%',#{userName},'%')
            <if test="userRole !=null and userRole !=''">
             and userRole = #{userRole}
            </if>    
    </select>

2.where---条件符合则自动加上where 且去掉第一个and(如果有and)

<!-- where 条件符合则自动加上where 且去掉第一个and-->
    <select id="getUser" resultType="Person" parameterType="Person">
        select * from smbms_user 
        <where>
            <if test="userName !=null and userName !=''">
                and userName=#{userName}
            </if>
        </where>
    </select>

3.set---可以更新一个或多个值，并且条件不成立为自动去掉多余的逗号

<!-- set可以更新一个或多个值，并且条件不成立为自动去掉多余的逗号 -->
    <update id="updateUser"  parameterType="Person">
        update smbms_user 
        <set>
            <if test="userName !=null and userName !=''">
                 userName=#{userName},
            </if>
            <if test="userPassword !=null and userPassword !=''">
                 userPassword=#{userPassword}
            </if>
        </set>
        where id=#{id}
    </update>

4.trim---prefix前缀   prefixOverrides去掉前缀             suffix后缀   suffixOverrides去掉后缀

<!-- trim 去掉and 加上where     prefix前缀   prefixOverrides去掉前缀             suffix后缀   suffixOverrides去掉后缀  -->
    <select id="where" parameterType="Person" resultType="Person">
        select * from smbms_user
        <trim prefix="where" prefixOverrides="and" suffix="" suffixOverrides="">
            <if test="userName !=null and userName !=''">
                and userName=#{userName}
            </if>
        </trim>
    </select>

5.choose---哪个分支条件成立就拼接哪个 , 都不成立就执行otherwise分支(相当于switch case default)

<!-- 哪个分支条件成立就拼接哪个         都不成立就执行otherwise分支 -->
    <select id="choose" parameterType="Person" resultType="Person">
        select * from smbms_user where i=1
        <choose>
             <when test="userName !=null and userName !=''">
                 and userName=#{userName}
             </when>
             <when test="userPassword !=null and userPassword !=''">
                 and userPassword=#{userPassword}
             </when>
             <otherwise>
                 and phone=#{phone}
             </otherwise>
        </choose>
    </select>

6.foreach---作用等同于in(?,?,?)

<!-- 等同于in(?,?,?) -->
    <select id="foreach"  resultType="Person">
        select * from smbms_user where userRole in 
        <foreach collection="list" item="roleid" open="(" separator="," close=")">
            #{roleid}
        </foreach>     
    </select>

 扩展

foreach实现多对多查询：

<!-- 多个供应商对应多个订单 -->
    <select id="forprobill"  resultMap="probill">
        select b.*,p.* from smbms_provider p,smbms_bill b where p.id=b.providerId and p.id in 
        <foreach collection="array" item="roleid" open="(" separator="," close=")">
            #{roleid}
        </foreach>     
    </select>
     <resultMap type="Provider" id="probill">
        <id property="id" column="id"/>
        <collection property="billList" ofType="Bill">
            <id  property="id" column="id"/>
            <result property="productName" column="productName"/>
        </collection>
    </resultMap> 

传入map多值查询

<!-- map传参多个值      in的参数对应collection参数 为map对应的key值rmap   gender值为map对应的key值gender  区分大小写-->
    <select id="userMap" resultType="Person" parameterType="Map">
        select * from smbms_user where userRole in 
        <foreach collection="rmap" item="roid" open="(" separator="," close=")">
            #{roid}
        </foreach>
         and gender=#{gender} 
    </select>