MySQL 从多个表中选择

Question

im trying to select data from multiple tables, now i am fine with doing it with two tables as i do a query like so:

$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)"
);

But see now, i want to select data from a third table, however this third table does not have relationship such as primary key between the first two tables, so i simply want to just pull data from it and form any sort of link with a "JOIN".

How would simply add the third to this query?

Thanks

Answer 1

You could use 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"
);

I used this other post to find the idea.

More infos here .

Answer 2

在您的查询中添加左连接。

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"
);