Mysql Union如何检查行是否存在？

Question

OK this is bit complicated because my tables are not referenced or combined or to be matched with each other so I cant use JOIN's. I am building a search form that would simply match search keyword in multiple tables.

The issue I have is that I have to generate news item link depending from which table the result came but I cant find a hook. MySql union works perfect except that I cant check if data is from table a or table b.

here is short version 
SELECT  i.title,i.category FROM table_a  WHERE REGEXP 'news'
UNION 
SELECT i.title,i.category FROM table_b WHERE REGEXP 'news'

now , my table A has 36 rows and table B has 34 , one more difference is that table A has row name extra_field which I wanted to check and based on that switch my link.

php switch after query could be something like

foreach($rows as $row) :
if($row->extra_field):
$link = 'index.php?".$row->category.$row->title".html'
else:
$link = 'index.php?".$row->title".html'
endif;
endforeach;

So is there a way to check in my UNION sql if that row exists? I know how to check if row exists but how to do that in UNION?

Please help. Thank you!

Answer 1

Using your short version as an example, you could add an extra column to the query:

SELECT  i.title,i.category,'a' as source FROM table_a  WHERE REGEXP 'news'
UNION 
SELECT i.title,i.category, 'b' as source FROM table_b WHERE REGEXP 'news'

Then in your code you could check the 'source' column.