查找表名

Question

i've 8 tables.. assume it as x1,x2...x8. these tables have similar structure with fields as: id,content,pageview.

Pageview count the number of views of particular id. post's are stored in rows with particular id's.

i want to find first top 10 post on the basis of pageview from these 8 tables.

i used :

$sql="select id,content from x1,x2,x3,x4,x5,x6,x7,x8 ORDER by pageview;"

results comes up.ok! suppose results are like

Id Content
13 this is just one 19 okay what to say .. .. .

in this result i want to find this ID:19 belongs to which table? I can run loops to match content but that wont be fast enough and good logic..

any solution to find tablename of particular id?

Answer 1

Your sample query will not run as is if you have the same field names in each table. Not to mention that you're producing a cartesian product since you're not joining on any of your fields.

I think you might be looking for a UNION instead:

select *
from (
   select 'x1' as whichtable, id, content, pageview from x1
   union
   select 'x2' as whichtable, id, content, pageview from x2
   ...
   union
   select 'x8' as whichtable, id, content, pageview from x8
) t
order by pageview

Then you can use the whichtable field to see which table the result came from.

Here is a sample SQL Fiddle Demo .

---

Just reread your post, and if you're looking for which table contains ID 19, then you can add a where clause to the above query:

select *
from (
   select 'x1' as whichtable, id, content, pageview from x1
   union
   select 'x2' as whichtable, id, content, pageview from x2
   ...
   union
   select 'x8' as whichtable, id, content, pageview from x8
) t
where id = 19
order by pageview