Fetch and match data from 2 tables?

[marcus123]

My PHP sucks big time please help!

I have 2 tables A and B which both contain column called TID

How can I fetch TIDs from column A that are not in the column B?

[Yumi]

2 tables A and B
[...]
column A [...] column B?

Trying to treat tables as columns may be your problem...

Assuming you meant 'table' throughout, there may be a few ways to write the SQL. Perhaps the most obvious is a correlated query:

SELECT tid FROM A WHERE tid NOT IN (SELECT tid FROM B)

If the tid columns are unique, a join could also work:

SELECT A.tid FROM A
LEFT JOIN B ON A.tid=B.tid
WHERE B.tid IS NULL

[marcus123]

Thanks buddy for reply.

Here is what I mean. I have a table called Ads which has a column called tid right. This TID column stores tids that correspond to forum real TIDs

I would like to fetch all thread tids and then all ads tids compare them and then output Thread tids that are not in the Ads tid column.

$query = $db->query("
        SELECT t.tid
        FROM ".TABLE_PREFIX."threads t
        WHERE t.tid NOT IN (how to fetch ads tid from here)
    ");

When I fetch tids they all show like one long number. How to put a comma in the middle to use it in NOT IN expression

---

$query2 = $db->query("
        SELECT t.tid
        FROM ".TABLE_PREFIX."threads t
		WHERE t.tid NOT IN (SELECT a.tid
        FROM ".TABLE_PREFIX."ads a)
    ");

Is this OK to use? Looks ugly to me!

[Omar G.]

Well it looks kind of beautiful to me.

[Yumi]

I'm not sure what you mean by "ugly".
Be aware that if you have a lot of threads, that query could be expensive (you'll need to test that), if it's run often.

[marcus123]

I mean that looks like it's gonna generate a ton of queries! I have like 4000+ threads + as many ads.

How to fetch thread tids separately to only generate one query and then use that value or array in this other query?

Is there a way to call $tids from custom page?

[Destroy666]

How exactly can one query with a subquery generate ton of queries?

[marcus123]

D666 do you think it will only generate one query? Since this is a custom page that I will only use one time I don't think it will put too much stress on the script right?

[Cedric]

This user has been denied support.

D666 do you think it will only generate one query? Since this is a custom page that I will only use one time I don't think it will put too much stress on the script right?

It doesn't depend on the number of threads. The number of queries depends upon how many times $db->query(); method is executed.

So if you execute it once, only 1 query will be generated.

[Omar G.]

Depending on the query it may be expensive to run it.

But since you are only going to run it once (apparently) just do it and be done with it.