Question

或许我很久没做左撇子JOIN了但我很困惑

这是我的桌子:

Table: user_phones

user    phone       carrier
----------------------------
danny   5045551234  Verizon
mom     5551234567  T-Mob
tony    5121234567  T-Mob

Table carriers

carrier    email_exchange
--------------------------
Verizon    vtext.com
T-Mob      tmomail.net

这是我的问题:

SELECT user, CONCAT(phone,  @ , email_exchange) AS sms
LEFT JOIN carriers ON (user_phones.carrier = carriers.carrier)
FROM user_phones

我不断回溯:

LEFT JOIN carriers ON (user_phones.carrier = carriers.carrier) FROM user_phones

我知道这是对笨蛋的监督,但变式没有帮助(括号中写有 ON 条款,等等)没有效果。

我该往哪儿滑呢?

Answer 1

您错过了 FROM user_phones 。

SELECT a.`user`, 
       CONCAT(a.`phone`,  @ , b.`email_exchange`) AS sms
FROM user_phones a LEFT JOIN carriers b 
        ON a.carrier = b.carrier

Answer 2

将您的 FROM 条款放在您的 LEFT JOIN 之前

SELECT `user`, CONCAT(phone,  @ , email_exchange) AS sms
FROM user_phones LEFT JOIN carriers ON user_phones.carrier = carriers.carrier

一个小建议是,在您的 carriers 表格中使用自动递增 id 字段,更新 user_phones.carrier ,以持有这些 id ,并加入其中。

Answer 3

尝试 :

SELECT user, CONCAT(phone,  @ , email_exchange) AS sms
FROM user_phones
LEFT JOIN carriers ON (user_phones.carrier = carriers.carrier)

""http://www.w3schools.com/sql/sql_sql_join_left.asp" rel="nofollow" >w3schools - Left join

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