如何使用mysql从这三个表中提取所需的数据？

Question

很抱歉，我正在努力找出正确的SQL来从这三个表中提取所需的数据......

users:- id, firstname, lastname, email, live
contracts:- id, userid, contractid
userstage:- id, userid, stageid, statusid

我需要来自用户的名字，姓氏，电子邮件，直播 并从合同中收缩， 和来自userstage的statusid

WHERE users.live =1 AND contracts.contractid = 1 AND userstage.statusid <>4 (not equal to 4)

谢谢。

Answer 1

这是非常基本的SQL。别忘了你的问题是什么。您可能希望根据需要更改为OUTER JOIN（左或右）。

SELECT u.firstname, u.lastname, u.email, u.live, c.contractid, us.statusid
FROM users AS u
INNER JOIN contracts AS c ON u.id = c.userid
INNER JOIN userstage AS us ON u.id = us.userid
WHERE u.live = 1 AND c.contractid = 1 AND us.statusid <> 4

Answer 2

根据您在某些用户没有合同等时的操作，您可以从：

开始

SELECT  firstname, lastname, email, live, contractid, statusid 
FROM users
JOIN contracts ON contracts.userid = users.id
JOIN userstage ON userstage.userid = users.id
WHERE users.live =1 AND contracts.contractid = 1 AND userstage.statusid <>4 (not equal to 4)