Conditional Expressions

caution

This feature is available starting from QQL 5.6.

Basic

Similarly to ternary operators in Python, you can use if ... else conditional expressions to test a simple condition:

note

Condition under if must be a boolean expression.

select 'few' if n < 3 else 'many', n
array join [0, 1, 2, 3, 4] as n

Switch Case

Similarly to SQL, you can use QQL conditional expressions to test several cases:

Synopsis

CASE expression
WHEN value THEN result
[WHEN...]
[ELSE result]
END

note

• Types of THEN and ELSE expressions must be equal (for example, all float or all arrays of int32).
• If several WHEN expressions are true, the first corresponding THEN result is selected.

select case n
  when 0 then 'zero'
  when 1 then 'one'
  when 2 then 'two'
  else 'many'
end, n
array join [0, 1, 2, 3, 4] as n

If case expression is empty, expressions under WHEN must return boolean values:

select case
  when n == 0 then 'zero'
  when n == 1 then 'one'
  when n == 2 then 'two'
  else 'many'
end, n
array join [0, 1, 2, 3, 4] as n

-- another format of writing the expression in the first section using Switch Case keywords:
select case when n < 3 then 'few' else 'many' end, n
array join [0, 1, 2, 3, 4] as n

with
(case size(entries)
  when 1 then 'one'
  when 2 then 'two'
  when 3 then 'three'
  else 'many'
end) as t
select 
  t, count{}()
from KRAKEN
group by t

select case
  when size(entries[this is L1Entry]) > 0 
    then 'L1'
  when size(entries[this is L2EntryNew or this is L2EntryUpdate]) > 0 
    then 'L2'
  end, 
  entries
from KRAKEN