SELECTING with multiple WHERE conditions on same column

Question

Ok, I think I might be overlooking something obvious/simple here... but I need to write a query that returns only records that match multiple criteria on the same column...

My table is a very simple linking setup for applying flags to a user ...

ID   contactid  flag        flag_type 
-----------------------------------
118  99         Volunteer   1 
119  99         Uploaded    2 
120  100        Via Import  3 
121  100        Volunteer   1  
122  100        Uploaded    2

etc... in this case you'll see both contact 99 and 100 are flagged as both "Volunteer" and "Uploaded"...

What I need to be able to do is return those contactid's ONLY that match multiple criteria entered via a search form...the contactid's have to match ALL chosen flags... in my head the SQL should look something like:

SELECT contactid 
 WHERE flag = 'Volunteer' 
   AND flag = 'Uploaded'...

but... that returns nothing... What am I doing wrong here?

Solution 1

You can either use GROUP BY and HAVING COUNT(*) = _:

SELECT contact_id
FROM your_table
WHERE flag IN ('Volunteer', 'Uploaded', ...)
GROUP BY contact_id
HAVING COUNT(*) = 2 -- // must match number in the WHERE flag IN (...) list

(assuming contact_id, flag is unique).

Or use joins:

SELECT T1.contact_id
FROM your_table T1
JOIN your_table T2 ON T1.contact_id = T2.contact_id AND T2.flag = 'Uploaded'
-- // more joins if necessary
WHERE T1.flag = 'Volunteer'

If the list of flags is very long and there are lots of matches the first is probably faster. If the list of flags is short and there are few matches, you will probably find that the second is faster. If performance is a concern try testing both on your data to see which works best.

Solution 2

Use:

  SELECT t.contactid
    FROM YOUR_TABLE t
   WHERE flag IN ('Volunteer', 'Uploaded')
GROUP BY t.contactid
  HAVING COUNT(DISTINCT t.flag) = 2

The key thing is that the counting of t.flag needs to equal the number of arguments in the IN clause.

The use of COUNT(DISTINCT t.flag) is in case there isn't a unique constraint on the combination of contactid and flag -- if there's no chance of duplicates you can omit the DISTINCT from the query:

  SELECT t.contactid
    FROM YOUR_TABLE t
   WHERE flag IN ('Volunteer', 'Uploaded')
GROUP BY t.contactid
  HAVING COUNT(t.flag) = 2

Solution 3

Consider using INTERSECT like this:

SELECT contactid WHERE flag = 'Volunteer' 
INTERSECT
SELECT contactid WHERE flag = 'Uploaded'

I think it it the most logistic solution.

Solution 4

can't really see your table, but flag cannot be both 'Volunteer' and 'Uploaded'. If you have multiple values in a column, you can use

WHERE flag LIKE "%Volunteer%" AND flag LIKE "%UPLOADED%"

not really applicable seeing the formatted table.

Solution 5

Try to use this alternate query:

SELECT A.CONTACTID 
FROM (SELECT CONTACTID FROM TESTTBL WHERE FLAG = 'VOLUNTEER')A , 
(SELECT CONTACTID FROM TESTTBL WHERE FLAG = 'UPLOADED') B WHERE A.CONTACTID = B.CONTACTID;

View more solutions

Comments

[Johar Zaman]

This statement is not working because flag cannot be equal to 'Volunteer' and 'Upload' at the same time. You can use OR operator instead of AND and it will work.

[OMG Ponies]

The problem with JOINs is if there's more than one record of a contactid associated with the "Uploaded" flag, there'll be duplicates for the T1 references.

[Kildareflare]

I don't believe this will return the results the OP desired. The contactIds need to match ALL flags, not one or more of them.

[kero]

This will show all entries that are Volunteer OR Uploaded but he wants entries that are twice in and have each once

[MickyD]

Consider improving your answer. Code-only answers may fall under 'Very Low Quality' ...and are candidates for deletion....We've always touted that we aren't a code factory. We are the people who teach others to fish. Code-only answers only feed a person for a day

[Bangash]

SELECT contact_id FROM your_table WHERE ( flag IN ('Volunteer', 'Uploaded', ...) and one_type = sometype_one ) AND flag IN ('someOtherVolunteer', 'Uploaded', ...) and second_type = sometype_two GROUP BY contact_id HAVING COUNT(*) = 2 Sir i have same senario like above query, but it's returning null. zero rows.

[Sri]

In case of self join, for N number of values, you'll need N self join. In that example, what if you have to get the results with all these three flags "Uploaded", "Volunteer" and "Via Import " in it? So, i think using GROUP BY with HAVING COUNT makes more sense.

[linkonabe]

Since the questioner tagged mysql, I think its good to point out that INTERSECT doesnt work for MySql

[JulieC]

The questioner may have tagged mysql, but thumbs up for this TSQL user this worked swimmingly for.