SQL Query to find unique values across multiple groups - mysql

Question

So i have a table in the format of:
Name, url, xpath, value
The problem is Name A, B, and F have a url U1 and xpath X1 that are the same (don't care about value).
Name C, D, E do not have that url U1 or did not have xpath X1.
Name B, C, D, E may share U2 and X2
I am trying to find the best way to find where the URL and xpath exist in all Names (A-F).
I didn't know if i should create a temp table with all the unique values where URL and xpaths match. then use that temp table to go through all the names and if all the names have that URL and Xpath then add it to a second temp table, then i would just return all the results from the final temp table.
Thanks!
Here is some example data:
Name, URL, Xpath, value
John, /MyAttributes.xml, /attribute/arms, 2
John, /MyAttributes.xml, /attributes/legs, 2
John, /MyQualities.xml, /qualities/race, human
Derek, /MyAttributes.xml, /attribute/legs, 2
Derek, /MyQualities.xml, /qualities/race, non-human
So the names could grow to have hundreds of names, and the information i am trying to gather would be that "/MyAttributes.xml, /attributes/legs" exists in both John & Derek, and as the db grows i still need to be able to see which url with xpath exists across all names.
Hopefully that helps providing more data.

Answer 1

Try this:
select
url,
xpath
from table
group by
url,
xpath
having
max(case when name='A' then
1
else
0
end) +
max(case when name='B' then
2
else
0
end) +
max(case when name='C' then
4
else
0
end) +
max(case when name='D' then
8
else
0
end) +
max(case when name='E' then
16
else
0
end) +
max(case when name='F' then
32
else
0
end) = 63;

Answer 2

Here's a variation on the answer submitted by Mark Bannister:
SELECT t.url
FROM
myTable t
CROSS JOIN (SELECT COUNT(DISTINCT name) AS cnt FROM myTable) x
GROUP BY t.url
HAVING COUNT(DISTINCT t.name) = MAX(x.cnt);

Answer 3

To find all urls that exist for all names, try:
select url
from myTable
group by url
having count(distinct name) = (select count(distinct name) from myTable)
To find xpaths that exist for all names, swap xpath and url in the above query.

Answer 4

So this is what i ended up doing. Thanks to everyone who helped. If you know a good way to optimize this that would be AWESOME.
To summarize i did end up creating a temp table. i then go through all the unique results. and see if that url + xpath exists on all the unique names. then if it does i insert it into my temp table, where i just dump that out at the end.
BEGIN
DECLARE bDone INT;
DECLARE var1 VARCHAR(845);
DECLARE var2 VARCHAR(45);
DECLARE var3 VARCHAR(800);
DECLARE curs CURSOR FOR SELECT DISTINCT CONCAT(url, xpath), url, xpath FROM myTable;
DECLARE CONTINUE HANDLER FOR NOT FOUND SET bDone = 1;
DROP TEMPORARY TABLE IF EXISTS tblResults;
CREATE TEMPORARY TABLE IF NOT EXISTS tblResults (
url VARCHAR(45),
xpath VARCHAR(800)
);
OPEN curs;
SET bDone = 0;
REPEAT
FETCH curs INTO var1, var2, var3;
IF
(
SELECT
COUNT(DISTINCT name)
FROM myTable as l
WHERE
l.url = var2 AND
l.xpath = var3
) = (
SELECT
COUNT(DISTINCT name)
FROM myTable
) THEN
INSERT INTO tblResults VALUES (var2, var3);
END IF;
UNTIL bDone END REPEAT;
CLOSE curs;
SELECT * FROM tblResults;
END