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sql query select on two criteria, same field?

Posted on 2009-07-02
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Last Modified: 2013-12-07
I want an sql SELECT that will select on the same field
and will use two, separate criteria for that field.

The result should be the subset that satisfies BOTH criteria.

The example below does not work.

How do I do this?


select * from cam where cust='1' and cust='2'

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Question by:pillmill
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16 Comments
 
LVL 75

Expert Comment

by:Aneesh Retnakaran
ID: 24765190
select * from cam where cust='1' or  cust='2'
0
 
LVL 75

Expert Comment

by:Aneesh Retnakaran
ID: 24765196
you never can 1 = 2
0
 
LVL 40

Expert Comment

by:mrjoltcola
ID: 24765204
You can also use IN()

where cust in('1', '2')
0
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Author Comment

by:pillmill
ID: 24765716
Thanks. Both where cust in('1', '2')  and  select * from cam where cust='1' or  cust='2'  are producing the WRONG result.

I want the intersection of the sets of results produced by these two queries:

1. select * from cam where cust='1'

2. select * from cam where cust='2'
0
 
LVL 46

Expert Comment

by:Kent Olsen
ID: 24765759
Hi pillmill,

The intersection will be a NULL set.  "cust" can be 1, or it can be 2, but it can't be both.


Kent
0
 

Author Comment

by:pillmill
ID: 24765896
Thanks. Here are the records:

table cam:

cust     cama
1          a
1           b
2          a
2          c


I want the query to return the value "a" .  The value "a" is the one
which is the same between cust 1 and 2.
0
 
LVL 46

Expert Comment

by:Kent Olsen
ID: 24766043

Hmm....  There are a lot of variables here.  Can 'a occur more than once per customer number?  Will it occur only twice?  Are more values than 1 and 2 possible for cust, etc.

Here's one solution:

SELECT cama, count() as c FROM mytable
GROUP BY cama
HAVING c > 1;


Kent
0
 
LVL 11

Expert Comment

by:Andytw
ID: 24766127
Try:
SELECT cama FROM cam WHERE cust = 1
INTERSECT
SELECT cama FROM cam WHERE cust = 2;
 
or
 
SELECT cama c1
FROM cam WHERE cust = 1
WHERE EXISTS ( SELECT NULL
               FROM cam c2
               WHERE c1.cama = c2.cama
                 AND c1.cust <> c2.cust )
  

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0
 
LVL 32

Expert Comment

by:awking00
ID: 24766220
I suspect your problem may be little more complex than that indicated by your example. Are you trying to find values that exist for more than one customer, that exist for every customer, or do you want entire records (or perhaps more than one field) where those instances occur? Perhaps you could post some more relevant sample data and what your expected output should be.
0
 

Author Comment

by:pillmill
ID: 24766678
SELECT cama c1
FROM cam WHERE cust = 1
WHERE EXISTS ( SELECT NULL
               FROM cam c2
               WHERE c1.cama = c2.cama
                 AND c1.cust <> c2.cust )

produces a MySQL error:

Error Code : 1064
You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'WHERE exists ( SELECT NULL
0
 

Author Comment

by:pillmill
ID: 24766712
Record "a" is the common element.  

0
 
LVL 32

Expert Comment

by:awking00
ID: 24766861
Change "where exists" to "and exists".
0
 
LVL 46

Accepted Solution

by:
Kent Olsen earned 2000 total points
ID: 24766880
Hi Pill,

In this simple example, the cleanest SQL is an inner join.

SELECT cama
FROM mytable t0, mytable t1
WHERE t0.cama = t1.cama
  AND t0.cust = 1
  AND t0.cust = 2;

But that's probably not a lot of use with a larger data set.  Still, let's see where this goes.  :)


Kent
0
 
LVL 2

Expert Comment

by:kbac
ID: 24771030
select * from cam where
cama in (select cama from cam where cust='1' )
and
cama in (select cama from cam where cust='2' )
0
 

Author Closing Comment

by:pillmill
ID: 31599269
Thanks!
0
 
LVL 46

Expert Comment

by:Kent Olsen
ID: 24861181
Hi Pill,

For the record, there was a typo in my SQL, but it looks like you figured that out.   :)

Kent
0

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