MySQL 從多個表中選擇

Question

我試圖從多個表中選擇數據，現在我可以用兩個表來做，因為我做這樣的查詢：

$myquery = sql_query(
    "SELECT a.object_title, a.published_by, b.userid
     FROM table1 AS a 
     JOIN table2 AS b ON (a.published_by = b.userid)"
);

但是現在看，我想從第三個表中選擇數據，但是這個第三個表沒有前兩個表之間的主鍵等關系，所以我只想從中提取數據並形成任何類型的鏈接“加入”。

如何簡單地將第三個添加到此查詢中？

謝謝

Answer 1

您可以使用CROSS JOIN ：

$myquery = sql_query(
    "SELECT a.object_title, a.published_by, b.userid, c.whatever
     FROM table1 AS a 
     JOIN table2 AS b ON (a.published_by = b.userid)
     CROSS JOIN table3 AS c"
);

我用另一個帖子找到了這個想法。

更多信息在這里。

Answer 2

在您的查詢中添加左連接。

Answer 3

$myquery = sql_query(
            "SELECT a.object_title, a.published_by, b.userid, c.column_name
             FROM Table1 AS a 
             JOIN Table2 AS b ON (a.published_by = b.userid)
             CROSS JOIN Table3 AS c"
);