postgres 12 case array, range operator

SELECT * FROM test;

 a
---
 1
 2
 3


SELECT a,
       CASE WHEN a=1 THEN 'one'
            WHEN a=2 THEN 'two'
            ELSE 'other'
       END
    FROM test;

 a | case
---+-------
 1 | one
 2 | two
 3 | other

SELECT ... WHERE CASE WHEN x <> 0 THEN y/x > 1.5 ELSE false END;

Operator	Description	Example	Result
=	equal	ARRAY[1.1,2.1,3.1]::int[] = ARRAY[1,2,3]	t
<>	not equal	ARRAY[1,2,3] <> ARRAY[1,2,4]	t
<	less than	ARRAY[1,2,3] < ARRAY[1,2,4]	t
>	greater than	ARRAY[1,4,3] > ARRAY[1,2,4]	t
<=	less than or equal	ARRAY[1,2,3] <= ARRAY[1,2,3]	t
>=	greater than or equal	ARRAY[1,4,3] >= ARRAY[1,4,3]	t
@>	contains	ARRAY[1,4,3] @> ARRAY[3,1]	t
<@	is contained by	ARRAY[2,7] <@ ARRAY[1,7,4,2,6]	t
&&	overlap (have elements in common)	ARRAY[1,4,3] && ARRAY[2,1]	t
||	array-to-array concatenation	ARRAY[1,2,3] || ARRAY[4,5,6]	{1,2,3,4,5,6}
||	array-to-array concatenation	ARRAY[1,2,3] || ARRAY[[4,5,6],[7,8,9]]	{{1,2,3},{4,5,6},{7,8,9}}
||	element-to-array concatenation	3 || ARRAY[4,5,6]	{3,4,5,6}
||	array-to-element concatenation	ARRAY[4,5,6] || 7	{4,5,6,7}

Operator	Description	Example	Result
=	equal	int4range(1,5) = '[1,4]'::int4range	t
<>	not equal	numrange(1.1,2.2) <> numrange(1.1,2.3)	t
<	less than	int4range(1,10) < int4range(2,3)	t
>	greater than	int4range(1,10) > int4range(1,5)	t
<=	less than or equal	numrange(1.1,2.2) <= numrange(1.1,2.2)	t
>=	greater than or equal	numrange(1.1,2.2) >= numrange(1.1,2.0)	t
@>	contains range	int4range(2,4) @> int4range(2,3)	t
@>	contains element	'[2011-01-01,2011-03-01)'::tsrange @> '2011-01-10'::timestamp	t
<@	range is contained by	int4range(2,4) <@ int4range(1,7)	t
<@	element is contained by	42 <@ int4range(1,7)	f
&&	overlap (have points in common)	int8range(3,7) && int8range(4,12)	t
<<	strictly left of	int8range(1,10) << int8range(100,110)	t
>>	strictly right of	int8range(50,60) >> int8range(20,30)	t
&<	does not extend to the right of	int8range(1,20) &< int8range(18,20)	t
&>	does not extend to the left of	int8range(7,20) &> int8range(5,10)	t
-|-	is adjacent to	numrange(1.1,2.2) -|- numrange(2.2,3.3)	t
+	union	numrange(5,15) + numrange(10,20)	[5,20)
*	intersection	int8range(5,15) * int8range(10,20)	[10,15)
-	difference	int8range(5,15) - int8range(10,20)	[5,10)

https://www.postgresql.org/docs/current/functions-range.html