SELECTING with multiple WHERE conditions on same column

问题

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?

回答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.

回答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

回答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.

回答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.

回答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;

回答6:

SELECT contactid, Count(*) 
FROM <YOUR_TABLE> WHERE flag in ('Volunteer','Uploaded')  
GROUP BY contactid 
HAVING count(*)>1;

回答7:

Use this: For example:

select * from ACCOUNTS_DETAILS
where ACCOUNT_ID=1001
union
select * from ACCOUNTS_DETAILS
where ACCOUNT_ID=1002

回答8:

Change AND to OR. Simple mistake. Think of it like plain English, I want to select anything with that equals this or that.

回答9:

AND will return you an answer only when both volunteer and uploaded are present in your column. Otherwise it will return null value...

try using OR in your statement ...

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

回答10:

select purpose.pname,company.cname
from purpose
Inner Join company
on purpose.id=company.id
where pname='Fever' and cname='ABC' in (
  select mname
  from medication
  where mname like 'A%'
  order by mname
);

回答11:

your code :

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

will not work, for you did not declare the table name. the execution will return an error message.

and if you want both search query to display, your code should look something like this.

SELECT * FROM (your_table_name) WHERE flag = 'Volunteer' OR flag = 'Uploaded';

and not like this because it will always return false SELECT * FROM (your_table_name) WHERE flag = 'Volunteer' AND flag = 'Uploaded';

you can also do this

SELECT * FROM (your_table_name) 
WHERE flag = 'Volunteer' OR flag = 'Uploaded' 
ORDER BY contactid, flag asc;

(asc for ascending order, you can also change it to desc if you want it to display in descending order)

回答12:

Sometimes you can't see the wood for the trees :)

Your original SQL ..

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

Should be:

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

来源：https://stackoverflow.com/questions/4047484/selecting-with-multiple-where-conditions-on-same-column

标签

mysql

sql

aggregate-functions

where-clause