在兩個表的Mysql中聯接查詢

Question

我有兩個表：

ad ( id(int) , userid(int) ) ：用於存儲具有用戶列的廣告的表
adcat ( adid(int) , catid(int) ) ：用於存儲每個廣告（類別）的類別ID（類別adcat ( adid(int) , catid(int) )表

現在我要獲取的是由特定用戶發布的特定類別的廣告數量

范例：所有catid = 1且userid = 725的廣告

謝謝

Answer 1

SELECT * FROM ad 
LEFT JOIN adcat 
ON adcat.adid = ad.id
WHERE adcat.catid = 1 AND ad.userid = 725

Answer 2

嘗試使用JOIN和COUNT

SELECT COUNT(*) ads_total
  FROM ad a JOIN
       adcat c ON a.id = c.adid
 WHERE c.catid = 1 AND
       a.userid = 725

SQLFiddle

Answer 3

您需要加入表格：

SELECT * FROM ad INNER JOIN adcat ON adid=id WHERE catid=1 and userid=725;