javaweb-Mybatis动态sql

• if
  判断是否执行该sql

<select id="findUserById" resultType="user">
    select * from user where 
        <if test="id != null">
               id=#{id}
        </if>
    and deleteFlag=0;
</select>

• where
  连接sql语句

<select id="findUserById" resultType="user">
    select * from user 
        <where>
            <if test="id != null">
                id=#{id}
            </if>
            and deleteFlag=0;
        </where>
</select>

• foreach
  不确定进行几次sql时使用

    <insert id="insertBatch">
        insert into emp_expr(emp_id, begin, end, company, job) values
        <foreach collection="exprList" item="expr" separator=",">
            (#{expr.empId},#{expr.begin},#{expr.end},#{expr.company},#{expr.job})
        </foreach>
    </insert>