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GREATEST and LEAST in SQL standard

Tags:

sql

standards

My understanding is that GREATEST() and LEAST() are not part of the SQL standard, but are very common.

I'm wondering, is there a way to clone the functionality of GREATEST keeping within the SQL standard?

SELECT id, GREATEST(1,2,3,4,5,6,7) AS number FROM table

The fully query:

  SELECT SUBSTR(section,1,2) AS campus, 
           AVG(GREATEST(maximum - enrolled, 0)) AS empty 
    FROM sectionrun 
   WHERE coursenumber = '105' AND subject = 'ENGL' 
GROUP BY campus
like image 353
WalterJ89 Avatar asked Sep 25 '10 15:09

WalterJ89


Video Answer


2 Answers

GREATEST(1,2,3,4,5,6,7) AS number

can become

(select max(tmp) from (
        select 1 tmp from dual
        union all
        select 2 tmp from dual
        union all
        select 3 tmp from dual
        union all
        select 4 tmp from dual
        union all
        select 5 tmp from dual
        union all
        select 6 tmp from dual
        union all
        select 7 tmp from dual
) ) AS number          
like image 112
Never Sleep Again Avatar answered Sep 20 '22 08:09

Never Sleep Again


You can use the CASE expression:

  SELECT SUBSTR(section,1,2) AS campus, 
           AVG(CASE WHEN maximum - enrolled > 0 
                    THEN maximum - enrolled
                    ELSE 0
               END) AS empty 
    FROM sectionrun 
   WHERE coursenumber = '105' AND subject = 'ENGL' 
GROUP BY campus
like image 26
Aillyn Avatar answered Sep 24 '22 08:09

Aillyn