前言

小結

前言

小編最近在專案中接觸到一個超長的SQL語句,發現裡面的語法很豐富,可以拿出來記錄一下,當然也有將其中重複的部分進行刪減,方便博友們進行檢視分析。

展示SQL語句

    SQL語句查詢，作用是從兩張表 t_card_order 和 t_card_consume_info 中查詢出各自需要的欄位資訊。

      SELECT
            p.pay_time AS paymentCreateTime,
            p.thirdpart_trans_code AS thirdpartTransCode,
            o.id AS orderCode,
            '購卡' AS payType,           
            CASE o.card_type
              WHEN '1' THEN '儲值卡'
              WHEN '2' THEN '權益卡'
            END AS cardType
        FROM t_card_order o
          RIGHT JOIN t_order_payment p
            ON o.id = p.order_code
          LEFT JOIN t_movie_cinema c
            ON o.cinema_code = c.cinema_code
        WHERE            
            <if test="param.cinemaCodes != null">
                AND o.cinema_code in
                <foreach item="item" index="index" collection="param.cinemaCodes" open="
                  (" separator="," close=")">
                    #{item}
                </foreach>
            </if>           
            <choose>
                <when test="param.dateTag == 'week'">
                    AND DATE_SUB(CURDATE(), INTERVAL 7 DAY) <= DATE(p.pay_time)
                </when>
                <when test="param.dateTag == 'oneMonth'">
                    AND DATE_SUB(CURDATE(), INTERVAL 1 MONTH) <= DATE(p.pay_time)
                </when>
                <when test="param.dateTag == 'threeMonth'">
                    AND DATE_SUB(CURDATE(), INTERVAL 3 MONTH) <= DATE(p.pay_time)
                </when>
            </choose>
        UNION
        SELECT
            info.create_time AS paymentCreateTime,
            info.transaction_id AS thirdpartTransCode,
            info.id AS orderCode,
            '充值' AS payType,
            CASE info.card_type
              WHEN '1' THEN '儲值卡'
              WHEN '2' THEN '權益卡'
            END AS cardType
        FROM t_card_consume_info info
        LEFT JOIN t_movie_cinema c
        ON info.cinema_code = c.cinema_code
        WHERE info.consume_type = 0
            AND consume_comment != '購卡'
            AND consume_comment != '綁卡首次充值' 
 

分析SQL語句

   一、union語句

    注意：使用union語句，聯結的兩張表之間的欄位個數、名稱必須保持一致，否則會報錯

     -- 第一張表中的欄位如下：
            p.pay_time AS paymentCreateTime,
            p.thirdpart_trans_code AS thirdpartTransCode,
            o.id AS orderCode,
            '購卡' AS payType,           
            CASE o.card_type
              WHEN '1' THEN '儲值卡'
              WHEN '2' THEN '權益卡'
            END AS cardType
    -- 第二張表中的欄位如下：
            info.create_time AS paymentCreateTime,
            info.transaction_id AS thirdpartTransCode,
            info.id AS orderCode,
            '充值' AS payType,
            CASE info.card_type
              WHEN '1' THEN '儲值卡'
              WHEN '2' THEN '權益卡'
            END AS cardType
 

  二、條件語句

      三種條件語句：case、if和choose whenti

     ---case條件語句 
            CASE o.card_type
              WHEN '1' THEN '儲值卡'
              WHEN '2' THEN '權益卡'
            END AS cardType
     ---if條件語句 
            <if test="param.cinemaCodes != null">
                AND o.cinema_code in
                <foreach item="item" index="index" collection="param.cinemaCodes" open="
                  (" separator="," close=")">
                    #{item}
                </foreach>
            </if>    
       ---choose when條件語句 
            <choose>
                <when test="param.dateTag == 'week'">
                    AND DATE_SUB(CURDATE(), INTERVAL 7 DAY) <= DATE(p.pay_time)
                </when>
                <when test="param.dateTag == 'oneMonth'">
                    AND DATE_SUB(CURDATE(), INTERVAL 1 MONTH) <= DATE(p.pay_time)
                </when>
                <when test="param.dateTag == 'threeMonth'">
                    AND DATE_SUB(CURDATE(), INTERVAL 3 MONTH) <= DATE(p.pay_time)
                </when>
            </choose>
 

三、查詢結果圖

      欄位 為null值： orderCode、cardType等，產生的原因是左右外連線的結果：left join / right join

小結

通過一番總結，能夠讓自己對於SQL語句的查詢有更深刻的認識，同時也希望對大家有所幫助！

                                                                             感謝您的訪問！