Below is my current SELECT CASE statement:
SELECT CASE
WHEN edition = 'STAN' AND has9 = 1 THEN '9'
WHEN edition = 'STAN' AND has8 = 1 THEN '8'
WHEN edition = 'STAN' AND has7 = 1 THEN '7'
WHEN edition = 'STAN' AND hasOLD = 1 THEN 'OLD'
WHEN edition = 'SUI' AND has_s9 = 1 THEN 'S9'
WHEN edition = 'SUI' AND has_s8 = 1 THEN 'S8' ELSE 'S7' END AS version
I do not always want to repeat the edition = 'xxx' condition, such as
CASE WHEN edition = 'STAN' AND has9 = 1 THEN '9' ELSE WHEN has8 = 1 THEN '8' ELSE WHEN has7 = '7' ELSE WHEN edition 'SUI' AND has_s9 = 1 THEN 'S9' ELSE ...
In Excel this is fairly easy but how can I compile that in PostgreSQL?
Try this
SELECT CASE
WHEN edition = 'STAN' THEN
CASE
WHEN has9 = 1 THEN '9'
WHEN has8 = 1 THEN '8'
WHEN has7 = 1 THEN '7'
WHEN hasOLD = 1 THEN 'OLD'
END
WHEN edition = 'SUI' THEN
CASE
WHEN has9 = 1 THEN 'S9'
WHEN has8 = 1 THEN 'S8'
END
ELSE 'S7' END AS version
You can nest your case when.
By the way, when you make a case on a single field, you can do
case <field> when <value>
when <otherValue>
rather then
case when <field> = <value>
when <field> = <otherValue>
So
case edition
when 'STAN'
case when has9 = 1 then '9'
when has8 = 1 then '8'
when has7 = 1 then '7'
when hasOLD = 1 then 'OLD'
end
when 'SUI'
case when has_s9 = 1 then 'S9'
when has_s8 = 1 then 'S8'
end
else 'S7'
end as version
Postgres supports both syntax variants for CASE
: the "simple CASE" and the "searched CASE". Use a "simple CASE". And you can also nest to mix both variants:
SELECT CASE edition
WHEN 'STAN' THEN
CASE WHEN has9 = 1 THEN '9'
WHEN has8 = 1 THEN '8'
WHEN has7 = 1 THEN '7'
WHEN hasOLD = 1 THEN 'OLD'
-- no ELSE means ELSE NULL
END
WHEN 'SUI' THEN
CASE WHEN has_s9 = 1 THEN 'S9'
WHEN has_s8 = 1 THEN 'S8'
END -- no ELSE means ELSE NULL
ELSE 'S7'
END AS version;
To carry this one step further , you can switch constant and variable. Both are just expressions and can trade places in Postgres. Maybe not as easy to read and understand, but if you want the shortest code ...
SELECT CASE edition
WHEN 'STAN' THEN
CASE 1
WHEN has9 THEN '9'
WHEN has8 THEN '8'
WHEN has7 THEN '7'
WHEN hasOLD THEN 'OLD'
END
WHEN 'SUI' THEN
CASE 1
WHEN has_s9 THEN 'S9'
WHEN has_s8 THEN 'S8'
END
ELSE 'S7'
END AS version;
Aside: The syntax for CASE
statements in plpgsql (the procedural language) is slightly different. (Different thing, really!)