mysql - 使用 MySQL 3 个表中的数据查找总行数

Question

我正在尝试返回一个数字，但我认为查询需要覆盖 3 个表! 这是 3 个表格的简单示例(删除了几列)

table: opencall
---------------------------------
Users name | Site  | Phone      |
---------------------------------
John Smith | Leeds | 0113 1234567

table: userdb
-------------------------------------
emailAd         | site  | company   |
-------------------------------------
<a href="https://stackoverflow.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="532620362113373c3e323a3d7d303c3e" rel="noreferrer noopener nofollow">[email protected]</a> | Leeds | Yorks Post

table: company
----------------------------
pk_company_id  | division_name |
----------------------------
Yorks Post     | NORTH

现在，我想做的是找到 opencall 中“division_name”为“NORTH”的总行数，我尝试了一些查询，但它们总是返回一个太大的数字。

这是我尝试过的示例:

SELECT count(*) FROM opencall, company, userdb WHERE userdb.site = opencall.site AND userdb.company = company.pk_company_id AND opencall.logdatex BETWEEN 1385041200 and 1388041200 AND opencall.condition NOT IN (8,9,11,12,19) AND company.division_name = 'NORTH`'

但是，这会返回超过 8,000 的结果，就好像我刚刚输入:

SELECT count(*) FROM opencall where logdatex BETWEEN 1385041200 and 1388041200 AND condition NOT IN (8,9,11,12,19)

这将返回 128，因此我在限制 Division_name 时所追求的数字应该在 20 左右。任何有关此问题的帮助将不胜感激。

Answer 1

试试这个:

SELECT COUNT(DISTINCT oc.UsersName)
FROM opencall oc 
INNER JOIN userdb u ON oc.site = u.site
INNER JOIN company c ON u.company = c.pk_company_id
WHERE c.division_name = 'NORTH'AND oc.logdatex BETWEEN 1385041200 AND 1388041200 AND 
      oc.condition NOT IN (8,9,11,12,19)