Mysql 下面的SQL查询

表A具有当前的

值A

和

值B

：

Token     ValueA     ValueB 
ABC        SHOP Val1      
DEF        SHOP         Val2
GHI         SHIPP        Val3
JKL         SHIPP         Val2

表B包含所有数据转换：

Token      Value         Value2         Date                         Express
ABC     SHOP    Val1               2020-01-01             Yes
ABC.        SHOP       Val2               2020-02-01             Yes
ABC         SHIPP.      Val3               2020-03-01              Yes 
DEF          SHOP       Val1               2020-05-01               No
DEF          SHIPP       Val2               2020-04-01              No
DEF          SHIPP.      Val3               2020-03-01               No

我希望我的结果应包括表A中的最新数据，但增加表B中的具体日期：

Token     ValueA       Val1 Date       Val2 Date
ABC        SHOP . 2020-01-01       2020-02-01
DEF        SHOP          2020-05-01.      2020-04-01   
GHI         SHIPP         NULL          NULL
JKL         SHIPP        NULL           NULL

我的查询未按预期返回结果：

SELECT a.token,
              A.valueA,
              A.valueB,
              B.Express
       c.Date "SHOP DATE",
       d.Date “SHIP DATE"
FROM TableA A 
LEFT JOIN TABLEB B ON A.Token = B.Token
LEFT JOIN TABLEB C ON A.Token = B.Token
LEFT JOIN TABLEB D ON A.Token = B.Token
WHERE (c.value = ‘SHOP’ AND c.value2 = ‘Val1’)
  AND (c.value = ‘SHIP’ AND c.value2 = ‘Val13)
GROUP BY a.token
ORDER BY b.date DESC;

查询结果：

Token     ValueA       Val1 Date       Val2 Date
ABC        SHOP . 2020-01-01       2020-02-01
DEF        SHOP          2020-05-01.      2020-04-01   

---

将

WHERE

条件移动到

JOIN

中：

SELECT a.token,
              A.valueA,
              A.valueB,
              B.Express
       c.Date "SHOP DATE",
       d.Date "SHIP DATE"
FROM TableA A 
LEFT JOIN TABLEB B 
ON A.Token = B.Token

LEFT JOIN TABLEB C 
ON A.Token = B.Token
AND c.value = 'SHOP' AND c.value2 = 'Val1'
AND c.value = 'SHIP' AND c.value2 = 'Val3'

LEFT JOIN TABLEB D 
ON A.Token = B.Token

GROUP BY a.token
ORDER BY b.date DESC;

注意：该标记仅适用于Ruby ORM。另外，请努力想出一个更具描述性的标题。请参阅“”及其链接页面。“写一个标题，总结具体问题”。