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SQL: COUNT each of several values in one field

Posted on 2006-11-10
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Last Modified: 2012-05-05
I'm convinced there's an easy way to do this, but heck if I can figure it out.  My environment is Oracle.

I have a query that aggregates some of the data from a table so that the query result is a single row, like this:

TTL_COUNT | AVG_PRICE  |  AVG_AGE  |  TTL_PRICE  
       15        |       500       |       25       |       32672  

I have another field ('GRADE'), and I'd like to show the count of each value in that field (A-D).  So my result would look like:

TTL_COUNT | AVG_PRICE  |  AVG_AGE  |  TTL_PRICE  |  COUNT_A  | COUNT_B | COUNT_C | COUNT_D
       15        |       500       |       25       |       32672    |       6         |       8       |       0       |       1

The only way I've found make this work is with a subquery in my FROM clause for each value, which gets ridiculously long:

SELECT
   /*existing code above here*/
  COUNT(GRADE_A.key) AS COUNT_A,
  COUNT(GRADE_B.key) AS COUNT_B,
  COUNT(GRADE_C.key) AS COUNT_C,
  COUNT(GRADE_D.key) AS COUNT_D
FROM
  main_table,
  (SELECT key
     FROM main_table
     WHERE GRADE='A'
  ) GRADE_A,
  (SELECT key
     FROM main_table
     WHERE GRADE='B'
  ) GRADE_B,
  (SELECT key
     FROM main_table
     WHERE GRADE='C'
  ) GRADE_C,
  (SELECT key
     FROM main_table
     WHERE GRADE='D'
  ) GRADE_D
WHERE 1=1
  /*criteria for limiting records above here*/
  /*what follows are the joins that limit the subqueries to the same criteria the rest of the query uses*/
  AND main_table.key=GRADE_A.key(+)
  AND main_table.key=GRADE_B.key(+)
  AND main_table.key=GRADE_C.key(+)
  AND main_table.key=GRADE_D.key(+)


Any input is appreciated.
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Question by:Rakafkaven
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4 Comments
 
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Author Comment

by:Rakafkaven
ID: 17918344
If the lines at the bottom are confusing any non-Oracle users, think of them as LEFT JOINs from the main_table to the four subtables.  I'm assuming that if there is a better solution, it won't necessarily be Oracle-specific, which is why I tried this on the main DB page.
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Accepted Solution

by:
Ritesh_Garg earned 500 total points
ID: 17919516
There is a better way to do it:

SELECT
   /*existing code above here*/
  COUNT(DECODE(GRADE, 'A', 1, NULL)    COUNT_A,
  COUNT(DECODE(GRADE, 'B', 1, NULL)    COUNT_B,
  COUNT(DECODE(GRADE, 'C', 1, NULL)    COUNT_C,
  COUNT(DECODE(GRADE, 'D', 1, NULL)    COUNT_D,
FROM
  main_table
/

Count ignores null values therefore the decode will return 1 only when the GRADE = A and so on...

Hope this helps.
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LVL 5

Expert Comment

by:MrNetic
ID: 17921314
RacafKaven,

You could do something like,

Select count(*),ColumnName from TABLENAME

Group by ColumnName

It will answer you questions.

Best Regads,

Paulo Condeça.
0
 
LVL 4

Author Comment

by:Rakafkaven
ID: 17931390
Ritesh, that's perfect!  Don't know why I never think of using conditionals in my SQL.
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