Question

我试图从多个表中选择数据，现在我可以使用两个表进行，因为我这样做了一个查询：

$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)"
);

但是现在看，我想从第三个表中选择数据，但是这个第三个表没有关系，比如前两个表之间的主键，所以我只是想从中提取数据并形成任何类型的链接到＆＃34;加入＆＃34;。

如何简单地将第三个添加到此查询？

由于

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this other post找到了这个想法。

更多信息here。

Answer 2

在你的内部添加查询左连接。

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"
);

MySQL从多个表中选择

3 个答案: