Find only user-defined check constraints in Oracle ALL_CONSTRAINTS - sql

Question

Consider this table definition:
CREATE TABLE foo (
a int not null, -- Implicit not null constraint
b int check (b is not null), -- Explicit not null constraint
c int check (c > 1) -- Explicit constraint
);
I want to discover all the explicit check constraints, i.e. constraints that the user defined in their DDL statement by using the CHECK syntax. Those constraints may or may not be named. In the above example, they're not named. How can I discover only the "explicit" check constraints, ignoring the implicit ones?
E.g. when I query ALL_CONSTRAINTS:
SELECT *
FROM all_constraints
WHERE constraint_type = 'C'
AND table_name = 'FOO';
I don't see any way to distinguish the explicitness/implicitness:
CONSTRAINT_NAME SEARCH_CONDITION GENERATED
---------------------------------------------------
SYS_C00120656 "A" IS NOT NULL GENERATED NAME
SYS_C00120657 b is not null GENERATED NAME
SYS_C00120658 c > 1 GENERATED NAME

Answer 1

I could of course make a heuristic on the unlikelyhood of someone using the exact "COLUMN_NAME" IS NOT NULL syntax (including double quote):
SELECT *
FROM all_constraints
WHERE constraint_type = 'C'
AND table_name = 'FOO'
AND search_condition_vc NOT IN (
SELECT '"' || column_name || '" IS NOT NULL'
FROM all_tab_cols
WHERE table_name = 'FOO'
AND nullable = 'N'
);
This gives me the wanted result:
CONSTRAINT_NAME SEARCH_CONDITION GENERATED
---------------------------------------------------
SYS_C00120657 b is not null GENERATED NAME
SYS_C00120658 c > 1 GENERATED NAME
I'm putting this as an answer here, as this might be good enough for some people, but I'd really like a more reliable solution.

Answer 2

SYS.CDEF$.TYPE# knows the difference between implicit and explicit check constraints. Implicit check constraints are stored as 7, explicit check constraints are stored as 1.
--Explicit constraints only.
select constraint_name, search_condition
from dba_constraints
where (owner, constraint_name) not in
(
--Implicit constraints.
select dba_users.username, sys.con$.name
from sys.cdef$
join sys.con$
on cdef$.con# = con$.con#
join dba_users
on sys.con$.owner# = dba_users.user_id
where cdef$.type# = 7
)
and constraint_type = 'C'
and table_name = 'FOO'
order by 1;
CONSTRAINT_NAME SEARCH_CONDITION
--------------- ----------------
SYS_C00106940 b is not null
SYS_C00106941 c > 1
This solution has the obvious disadvantage of relying on undocumented tables. But it does appear to be more accurate than relying on the text of the condition. Some implicit check constraints are not created with double quotes. I can't reproduce that issue, but I found it happening to the table SYS.TAB$.

Answer 3

Idea: You could compare table with its "shadow" counterpart. CREATE TABLE AS does not preserve user defined check constraints:
-- original table
CREATE TABLE foo (
id int PRIMARY KEY NOT NULL,
a int not null, -- Implicit not null constraint
b int check (b is not null), -- Explicit not null constraint
c int check (c = 1), -- Explicit constraint
d INT CONSTRAINT my_check CHECK (d = 3)
);
-- clone without data(it should be stored in different schema than actual objects)
CREATE TABLE shadow_foo
AS
SELECT *
FROM foo
WHERE 1=2;
-- for Oracle 18c you could consider private temporary tables
CREATE PRIVATE TEMPORARY TABLE ora$shadow_foo ON COMMIT DROP DEFINITION
AS
SELECT * FROM foo WHERE 1=2;
And main query:
SELECT c.*
FROM (SELECT * FROM all_constraints WHERE TABLE_NAME NOT LIKE 'SHADOW%') c
LEFT JOIN (SELECT * FROM all_constraints WHERE TABLE_NAME LIKE 'SHADOW%') c2
ON c2.table_name = 'SHADOW_' || c.table_name
AND c2.owner = c.owner
AND c2.search_condition_vc = c.search_condition_vc
WHERE c2.owner IS NULL
AND c.constraint_type = 'C'
AND c.owner LIKE 'FIDDLE%'
db<>fiddle demo