SQL query help

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tigercorp

668 posts

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#123303 2-Jul-2013 22:00

Before anyone asks, this isn't homework, its a potential aid to an unfortunately very real problem :D

I have a query which works fine that goes:
select stuff from table1 where id1 = 'string_id1' and id2 = 'string'

My problem is I have the values for string_id1 and string_id2 in another table i.e table2. So to be clear, table2 consists of 2 columns called string_id1 and string_id2.

I want the results of the query for each line in table2. What's the best way to do this?

alasta

6704 posts

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#848435 2-Jul-2013 22:11

I have a query which works fine that goes:
select stuff from table1 where id1 = 'string_id1' and id2 = 'string'

My problem is I have the values for string_id1 and string_id2 in another table i.e table2. So to be clear, table2 consists of 2 columns called string_id1 and string_id2.

I want the results of the query for each line in table2. What's the best way to do this?

If I'm understanding the problem correctly then you could try:

SELECT stuff FROM table1
WHERE id1 IN (SELECT string_id1 FROM table2)
AND id2 IN (SELECT string_id2 FROM table2)

sidefx

3711 posts

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#848438 2-Jul-2013 22:23

Or just use a join:

http://sqlfiddle.com/#!6/c006c/1

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tigercorp

668 posts

Ultimate Geek

#848464 3-Jul-2013 00:17

alasta:
SELECT stuff FROM table1
WHERE id1 IN (SELECT string_id1 FROM table2)
AND id2 IN (SELECT string_id2 FROM table2)

Thanks but no go, syntax errors.

sidefx: Or just use a join:

http://sqlfiddle.com/#!6/c006c/1

This is what I was originally going for but the select statement is actually a bit more complex containing multiple joined tables already. I can join my table2 to it but I obviously don't understand the relationships properly and get incorrect data returned.
I guess I was hoping there was some (really inefficient but workable) LOOP I could run.

dolsen

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#848493 3-Jul-2013 07:17

Or an older style that may be easier to put into the existing query depending on how it is written.

select t1.stuff from table1 t1, table2 t2
where t1.id1 = t2.id1
and t1.id2 = t2.id2

sittingduckz

680 posts

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#848507 3-Jul-2013 08:04

What about:

SELECT Table1.stuff FROM Table1 INNER JOIN Table2 ON (Table1.id2 = Table2.string_id2) AND (Table1.id1 = Table2.string_id1)

I'm not a complete idiot, I still have some parts missing.

tchart

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#848516 3-Jul-2013 08:18

It really depends what you are trying to achieve.

Alastas SQL query below is fine if you are just trying to find records in table1 which have corresponding id's in table2

SELECT stuff FROM table1
WHERE id1 IN (SELECT string_id1 FROM table2)
AND id2 IN (SELECT string_id2 FROM table2)

However its more efficient to do an "EXISTS" query.

And I'm sorry to say this but if you're having syntax errors on a basic query like this then you probably need to go on a SQL course. Not trying to be mean or anything but Alastas query is basic SQL 101 that you should be able to do. Is there no DBA or someone else at work you can ask for help?

If not try and break the query down into bits that work eg try id1 first like this

SELECT * FROM TABLE1
WHERE ID1 IN (SELECT ID1 FROM TABLE2)

Bear in mind that the IN statement only expects a list of single item values from the SUB-QUERY so you cant do WHERE ID1 IN (SELECT ID1, ID2 FROM TABLE2) or anything like that. Also ID1 in each table should be the same data type otherwise youre going to have more trouble since you need to cast/convert types first.

I would only use a join if the intention was to "join" the two tables and see the information side by side. And as Dolsen said its easier to start with the older join syntax then this new fandangled INNER/OUTER JOIN syntax. Look for Oracle join syntax examples as they mostly show the older syntax.

Trevor

sittingduckz

680 posts

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#848517 3-Jul-2013 08:30

If this is somewhere inside a bigger query, then we probably need to see the entire query to figure it out.

Did you create the database yourself or is it an existing one?

Maybe the structure of the db could be changed to make the query less complex?

I'm not a complete idiot, I still have some parts missing.

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tigercorp

668 posts

Ultimate Geek

#848525 3-Jul-2013 08:47

tigercorp: ...

sidefx: Or just use a join:

http://sqlfiddle.com/#!6/c006c/1

This is what I was originally going for but the select statement is actually a bit more complex containing multiple joined tables already. I can join my table2 to it but I obviously don't understand the relationships properly and get incorrect data returned.

I've received an (unexpected) early morning answer from one of the development team who has provided the correct JOIN conditions to make this work.

I'll mark this as answered, thanks for all the advice everyone!

sittingduckz

680 posts

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#848526 3-Jul-2013 08:49

tigercorp:
tigercorp: ...

sidefx: Or just use a join:

http://sqlfiddle.com/#!6/c006c/1

This is what I was originally going for but the select statement is actually a bit more complex containing multiple joined tables already. I can join my table2 to it but I obviously don't understand the relationships properly and get incorrect data returned.

I've received an (unexpected) early morning answer from one of the development team who has provided the correct JOIN conditions to make this work.

I'll mark this as answered, thanks for all the advice everyone!

Please share, I'm curious now.

I'm not a complete idiot, I still have some parts missing.