[Solved] SQL query to classify triangles into Equilateral, Isosceles, etc

by


Keep in mind that CASE statements are evaluated IN ORDER – the first WHEN clause that fits “wins” and no further evaluation is made. So:

with
     triangles ( A, B, C ) as (
       select 20, 20, 23 from dual union all
       select 20, 20, 20 from dual union all
       select 20, 21, 22 from dual union all
       select 13, 14, 30 from dual
     )
select A, B, C, 
       case
            when A+B <= C  or B+C <= A or C+A <= B then 'Not A Triangle'                
            when A    = B and B    = C             then 'Equilateral'
            when A    = B  or B    = C or A    = C then 'Isosceles'
            else                                        'Scalene'  
            end  as classification
from   triangles
;

  A   B   C   CLASSIFICATION
--- --- ---   --------------
 20  20  23   Isosceles
 20  20  20   Equilateral
 20  21  22   Scalene
 13  14  30   Not A Triangle

4 rows selected.

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solved SQL query to classify triangles into Equilateral, Isosceles, etc