mysql時間字符串按年/月/天/時分組查詢 -- date_format

FROM test

GROUP BY DATE_FORMAT( deteline, "%Y-%m-%d %H" ) 

查詢某天：

deteline, "%Y-%m-%d"

某時：

deteline, "%Y-%m-%d %H"

依次類推。

其實就是對dateline進行處理，然后再對處理后的數據分組

 

ex:統計每小時創建的個數

SELECT DATE_FORMAT( create_time, "%Y-%m-%d %H" ) as time , COUNT( * ) as count FROM pdca GROUP BY DATE_FORMAT( create_time, "%Y-%m-%d %H" )

 Ex2:比較時間

    <select id="queryByStatusAndTime" parameterType="map" resultMap="BaseResultMap">
        select
        <include refid="Base_Column_List"/>
        from pdca
        <where>

            begin_time is not null and end_time is not null

            <if test="userId != null and userId != '' ">
                and user_id=#{userId}
            </if>

            <if test="status != null">
                and status in
                <foreach collection="status" item="s" open="(" separator="," close=")">
                    #{s}
                </foreach>
            </if>

            <if test="finishedTime != null and finishedTime != ''">
 and date_format(finished_time, '%Y-%m')=date_format(#{finishedTime}, '%Y-%m') 22             </if>

            <if test="endTime != null and endtime != ''">
 and date_format(end_time, '%Y-%m-%d')=date_format(#{endTime}, '%Y-%m-%d') 26             </if>

            <if test="endTimeLt != null and endtimeLt != ''">
                and end_time &lt; #{endTimeLt}
            </if>

            <if test="endTimeGt != null and endtimeGt != ''">
                and end_time &gt; #{endTimeGt}
            </if>

            <if test="beginTime != null and beginTime != ''">
 and date_format(begin_time, '%Y-%m-%d')=date_format(#{beginTime}, '%Y-%m-%d') 38             </if>

            <if test="completion != null">
                and completion=#{completion}
            </if>
        </where>
    </select>