left join引用表命名

Question

表a所含字段：USER_NAME，USER_PHONE，MONTH

表b所含字段：MOBILE_PHONE,OFFICE, SALES_REGION, WORKER等多个字段，但只需要join这几个

left join出来只有表a的信息，表b没有合并进来，求大佬讲解下引用表命名的规则！！！

 

Answer 1

SELECT a. "USER_ NAME", a. "USER_ PHONE", a. "LOGIN_ TIME
b. OFFICE, b. SALES_ REGION， b . WORKER
FROM表a a
LEFT JOIN表b b
ON a.字段 = b.字段
WHERE  login_time  BETWEEN ' 2021-1-01' AND '2021-1-31'
GROUP BY USER_ NAME,USER_ _PHONE, LOGIN_ TIME , OFFICE, SALES_ REGION , WORKER