Db2 Developer-C 11.1

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.
select service_level from sysibmadm.env_inst_info;


SERVICE_LEVEL


DB2 v11.1.4.4


with boolstmt as
(
  select  'exists' stmt,
    exists(select 1 from sysibm.sysdummy1 where ibmreqd = 'N') as x
  from sysibm.sysdummy1
 )
select
 stmt,
 x,
 x is null "x is null",
 not x "NOT x",
 x = FALSE "x = FALSE",
 smallint(x) "smallint(x)",
 char(x) "char(x)"
from boolstmt


STMT
X
x is null
NOT x
x = FALSE
smallint(x)
char(x)


exists
0
1
0
0
0



with boolstmt as
(
  select  'exists' stmt,
    exists(select 1 from sysibm.sysdummy1 where ibmreqd = 'N') as x
  from sysibm.sysdummy1
  union all
  select  'count' stmt,
    (select count(*) from sysibm.sysdummy1 where ibmreqd = 'N') > 0 as x
  from sysibm.sysdummy1
 )
select
 stmt,
 x,
 x is null "x is null",
 not x "NOT x",
 x = FALSE "x = FALSE",
 smallint(x) "smallint(x)",
 char(x) "char(x)"
from boolstmt


STMT
X
x is null
NOT x
x = FALSE
smallint(x)
char(x)


count
0
0
1
1
0
FALSE

exists
null
1
null
null
null
null