Different value counts on same column - sql

Question

I am new to Oracle. I have an Oracle table with three columns: serialno, item_category and item_status. In the third column the rows have values of serviceable, under_repair or condemned.
I want to run the query using count to show how many are serviceable, how many are under repair, how many are condemned against each item category.
I would like to run something like:
select item_category
, count(......) "total"
, count (.....) "serviceable"
, count(.....)"under_repair"
, count(....) "condemned"
from my_table
group by item_category ......
I am unable to run the inner query inside the count.
Here's what I'd like the result set to look like:
item_category total serviceable under repair condemned
============= ===== ============ ============ ===========
chair 18 10 5 3
table 12 6 3 3

Answer 1

You can either use CASE or DECODE statement inside the COUNT function.
SELECT item_category,
COUNT (*) total,
COUNT (DECODE (item_status, 'serviceable', 1)) AS serviceable,
COUNT (DECODE (item_status, 'under_repair', 1)) AS under_repair,
COUNT (DECODE (item_status, 'condemned', 1)) AS condemned
FROM mytable
GROUP BY item_category;
Output:
ITEM_CATEGORY TOTAL SERVICEABLE UNDER_REPAIR CONDEMNED
----------------------------------------------------------------
chair 5 1 2 2
table 5 3 1 1

Answer 2

This is a very basic "group by" query. If you search for that you will find plenty of documentation on how it is used.
For your specific case, you want:
select item_category, item_status, count(*)
from <your table>
group by item_category, item_status;
You'll get something like this:
item_category item_status count(*)
======================================
Chair under_repair 7
Chair condemned 16
Table under_repair 3
Change the column ordering as needed for your purpose

Answer 3

I have a tendency of writing this stuff up so when I forget how to do it, I have an easy to find example.
The PIVOT clause was new in 11g. Since that was 5+ years ago, I'm hoping you are using it.
Sample Data
create table t
(
serialno number(2,0),
item_category varchar2(30),
item_status varchar2(20)
);
insert into t ( serialno, item_category, item_status )
select
rownum serialno,
( case
when rownum <= 12 then 'table'
else 'chair'
end ) item_category,
( case
--table status
when rownum <= 12
and rownum <= 6
then 'servicable'
when rownum <= 12
and rownum between 7 and 9
then 'under_repair'
when rownum <= 12
and rownum > 9
then 'condemned'
--chair status
when rownum > 12
and rownum < 13 + 10
then 'servicable'
when rownum > 12
and rownum between 23 and 27
then 'under_repair'
when rownum > 12
and rownum > 27
then 'condemned'
end ) item_status
from
dual connect by level <= 30;
commit;
and the PIVOT query:
select *
from
(
select
item_status stat,
item_category,
item_status
from t
)
pivot
(
count( item_status )
for stat in ( 'servicable' as "servicable", 'under_repair' as "under_repair", 'condemned' as "condemned" )
);
ITEM_CATEGORY servicable under_repair condemned
------------- ---------- ------------ ----------
chair 10 5 3
table 6 3 3
I still prefer #Ramblin' Man's way of doing it (except using CASE in place of DECODE) though.
Edit
Just realized I left out the TOTAL column. I'm not sure there's a way to get that column using the PIVOT clause, perhaps someone else knows how. May also be the reason I don't use it that often.