In Oracle 10g, how can I drop a unique constraint on a column without knowing the name of the constraint (e.g. a system generated name, which won't necessarily be the same across database instances)? Dropping and recreating the table isn't an option. Is it possible?
You can retrieve the constraint's name with:
SELECT CONSTRAINT_NAME
FROM USER_CONSTRAINTS WHERE TABLE_NAME = 'xxx'
AND CONSTRAINT_TYPE = 'U'
You can for instance create a stored procedure that executes the previous sql, stores its result in a variable and uses this variable in ALTER TABLE DROP CONSTRAINT
EDIT: e.g.:
BEGIN
FOR r IN (
SELECT TABLE_NAME, CONSTRAINT_NAME
FROM USER_CONSTRAINTS WHERE TABLE_NAME = 'xxx'
AND CONSTRAINT_TYPE = 'U') LOOP
EXECUTE IMMEDIATE REPLACE(REPLACE(
'ALTER TABLE #TABLE# DROP CONSTRAINT #CON#'
,'#TABLE#',r.TABLE_NAME)
,'#CON#',r.CONSTRAINT_NAME);
END LOOP;
END;
Related
So I have a query that should add Primary Key to the Id field:
IF NOT EXISTS(SELECT *
FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS
WHERE CONSTRAINT_TYPE = 'PRIMARY KEY' AND TABLE_NAME = 'CAL')
BEGIN
DROP INDEX IF EXISTS CAL$01 ON dbo.CAL;
ALTER TABLE BTS.dbo.CAL
ALTER COLUMN Intern INT NOT NULL;
ALTER TABLE BTS.dbo.CAL
ADD CONSTRAINT PK_CAL_Intern PRIMARY KEY (Intern);
CREATE INDEX CAL$01
ON CAL (Intern);
END
The problem is that when I chose all this code and execute (F5), I get this error:
Whereas when I'm choosing every statement one by one it works as expected:
I am sure that the IF works as expected
I tried to use GO between statements, it's not allowed.
I should execute this code on a large number of tables
Maybe I don't know something about how SQL Server Management Studio executes statements
Before a query is run it is parsed. This is why what you're doing is failing. SQL server is checking the details of the Intern before the script is run. At the point you start to try to run the script, Intern in the table BTS.dbo.CAL is NULLable, and so the script fails.
You can get around this by running the statement to create the primary key cosntraint in a separate scope:
IF NOT EXISTS(
SELECT *
FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS
WHERE CONSTRAINT_TYPE = 'PRIMARY KEY' AND TABLE_NAME = 'CAL'
)
BEGIN
DROP INDEX IF EXISTS CAL$01 ON dbo.CAL;
ALTER TABLE
BTS.dbo.CAL
ALTER COLUMN
Intern
INT NOT NULL;
EXEC sys.sp_executesql N'ALTER TABLE BTS.dbo.CAL ADD CONSTRAINT PK_CAL_Intern PRIMARY KEY (Intern);';
CREATE INDEX [CAL$01]
ON CAL (Intern);
END'
Even though question is answer, I just wanted to add one more option.
You can separate statments into two separate batches, so that your change is available to the subsequent batch
CREATE TABLE #test(a int null);
-- DDL Changes
if exists(SELECT 1)
BEGIN
ALTER TABLE #test ALTER COLUMN a int not null;
END
GO
-- Index changes
if exists(SELECT 1)
BEGIN
ALTER TABLE #test ADD CONSTRAINT PK_test PRIMARY KEY(a)
END
GO
I want to drop a foreign key from a table but I do not know its identifier.
I get the identifier from the SYSCAT.KEYCOLUSE table.
After that I try to use that identifier to drop the FK.
Getting identifier
SELECT keycoluse.CONSTNAME FROM SYSCAT.KEYCOLUSE keycoluse WHERE TABSCHEMA = 'USER1' AND TABNAME = 'TABLE1' AND COLNAME = 'ID_TABLE'
result = ID000000001
Dropping FK
ALTER TABLE TABLE1
DROP FOREIGN KEY (SELECT keycoluse.CONSTNAME FROM SYSCAT.KEYCOLUSE keycoluse WHERE TABSCHEMA = 'USER1' AND TABNAME = 'TABLE1' AND COLNAME = 'ID_TABLE');
this throw error: [Error Code: -104, SQL State: 42601]
But if I use the identifier I got before in this way, it works:
ALTER TABLE TABLE1
DROP FOREIGN KEY ID000000001;
In this way, it does not work:
ALTER TABLE TABLE1
DROP FOREIGN KEY 'ID000000001';
When I execute the SELECT to get the id, it gets a varchar 'ID000000001' and that gives the error.
¿Is there a way to cast the result of the SELECT into the same type that we have in this command?
ALTER TABLE TABLE1
DROP FOREIGN KEY ID000000001;
You cannot use a variable (returned by a subselect) or a literal where an identifier is required.
What you can do is generate a script from the query you have, although I cannot imagine why you would want to use such a complex approach to drop a single constraint:
SELECT
'ALTER TABLE', 'TABLE1',
'DROP FOREIGN KEY', keycoluse.CONSTNAME
FROM
SYSCAT.KEYCOLUSE keycoluse
WHERE
TABSCHEMA = 'USER1' AND TABNAME = 'TABLE1' AND COLNAME = 'ID_TABLE'
The query will return a correct ALTER statement. You can copy/paste it into your favourite client software or write results to a text file and execute it, for example, with
db2 -f mydropscript.sql
I have a table in Oracle with several constraints. When I insert a new record and not all constraints are valid, then Oracle raise only the "first" error. How to get all violations of my record?
CREATE TABLE A_TABLE_TEST (
COL_1 NUMBER NOT NULL,
COL_2 NUMBER NOT NULL,
COL_3 NUMBER NOT NULL,
COL_4 NUMBER NOT NULL
);
INSERT INTO A_TABLE_TEST values (1,null,null,2);
ORA-01400: cannot insert NULL into ("USER_4_8483C"."A_TABLE_TEST"."COL_2")
I would like to get something like this:
Column COL_2: cannot insert NULL
Column COL_3: cannot insert NULL
This would be also sufficient:
Column COL_2: not valid
Column COL_3: not valid
Of course I could write a trigger and check each column individually, but I like to prefer constraints rather than triggers, they are easier to maintain and don't require manually written code.
Any idea?
There no straightforward way to report all possible constraint violations. Because when Oracle stumble on first violation of a constraint, no further evaluation is possible, statement fails, unless that constraint is deferred one or the log errors clause has been included in the DML statement. But it should be noted that log errors clause won't be able to catch all possible constraint violations, just records first one.
As one of the possible ways is to:
create exceptions table. It can be done by executing ora_home/rdbms/admin/utlexpt.sql script. The table's structure is pretty simple;
disable all table constraints;
execute DMLs;
enable all constraints with exceptions into <<exception table name>> clause. If you executed utlexpt.sql script, the name of the table exceptions are going to be stored would be exceptions.
Test table:
create table t1(
col1 number not null,
col2 number not null,
col3 number not null,
col4 number not null
);
Try to execute an insert statement:
insert into t1(col1, col2, col3, col4)
values(1, null, 2, null);
Error report -
SQL Error: ORA-01400: cannot insert NULL into ("HR"."T1"."COL2")
Disable all table's constraints:
alter table T1 disable constraint SYS_C009951;
alter table T1 disable constraint SYS_C009950;
alter table T1 disable constraint SYS_C009953;
alter table T1 disable constraint SYS_C009952;
Try to execute the previously failed insert statement again:
insert into t1(col1, col2, col3, col4)
values(1, null, 2, null);
1 rows inserted.
commit;
Now, enable table's constraints and store exceptions, if there are any, in the exceptions table:
alter table T1 enable constraint SYS_C009951 exceptions into exceptions;
alter table T1 enable constraint SYS_C009950 exceptions into exceptions;
alter table T1 enable constraint SYS_C009953 exceptions into exceptions;
alter table T1 enable constraint SYS_C009952 exceptions into exceptions;
Check the exceptions table:
column row_id format a30;
column owner format a7;
column table_name format a10;
column constraint format a12;
select *
from exceptions
ROW_ID OWNER TABLE_NAME CONSTRAINT
------------------------------ ------- ------- ------------
AAAWmUAAJAAAF6WAAA HR T1 SYS_C009951
AAAWmUAAJAAAF6WAAA HR T1 SYS_C009953
Two constraints have been violated. To find out column names, simply refer to user_cons_columns data dictionary view:
column table_name format a10;
column column_name format a7;
column row_id format a20;
select e.table_name
, t.COLUMN_NAME
, e.ROW_ID
from user_cons_columns t
join exceptions e
on (e.constraint = t.constraint_name)
TABLE_NAME COLUMN_NAME ROW_ID
---------- ---------- --------------------
T1 COL2 AAAWmUAAJAAAF6WAAA
T1 COL4 AAAWmUAAJAAAF6WAAA
The above query gives us column names, and rowids of problematic records. Having rowids at hand, there should be no problem to find those records that cause constraint violation, fix them, and re-enable constraints once again.
Here is the script that has been used to generate alter table statements for enabling and disabling constraints:
column cons_disable format a50
column cons_enable format a72
select 'alter table ' || t.table_name || ' disable constraint '||
t.constraint_name || ';' as cons_disable
, 'alter table ' || t.table_name || ' enable constraint '||
t.constraint_name || ' exceptions into exceptions;' as cons_enable
from user_constraints t
where t.table_name = 'T1'
order by t.constraint_type
You would have to implement a before-insert trigger to loop through all the conditions that you care about.
Think about the situation from the database's perspective. When you do an insert, the database can basically do two things: complete the insert successfully or fail for some reason (typically a constraint violation).
The database wants to proceed as quickly as possibly and not do unnecessary work. Once it has found the first complaint violation, it knows that the record is not going into the database. So, the engine wisely returns an error and stops checking further constraints. There is no reason for the engine to get the full list of violations.
In the meantime I found a lean solution using deferred constraints:
CREATE TABLE A_TABLE_TEST (
COL_1 NUMBER NOT NULL DEFERRABLE INITIALLY DEFERRED,
COL_2 NUMBER NOT NULL DEFERRABLE INITIALLY DEFERRED,
COL_3 NUMBER NOT NULL DEFERRABLE INITIALLY DEFERRED,
COL_4 NUMBER NOT NULL DEFERRABLE INITIALLY DEFERRED
);
INSERT INTO A_TABLE_TEST values (1,null,null,2);
DECLARE
CHECK_CONSTRAINT_VIOLATED EXCEPTION;
PRAGMA EXCEPTION_INIT(CHECK_CONSTRAINT_VIOLATED, -2290);
REF_CONSTRAINT_VIOLATED EXCEPTION;
PRAGMA EXCEPTION_INIT(REF_CONSTRAINT_VIOLATED , -2292);
CURSOR CheckConstraints IS
SELECT TABLE_NAME, CONSTRAINT_NAME, COLUMN_NAME
FROM USER_CONSTRAINTS
JOIN USER_CONS_COLUMNS USING (TABLE_NAME, CONSTRAINT_NAME)
WHERE TABLE_NAME = 'A_TABLE_TEST'
AND DEFERRED = 'DEFERRED'
AND STATUS = 'ENABLED';
BEGIN
FOR aCon IN CheckConstraints LOOP
BEGIN
EXECUTE IMMEDIATE 'SET CONSTRAINT '||aCon.CONSTRAINT_NAME||' IMMEDIATE';
EXCEPTION
WHEN CHECK_CONSTRAINT_VIOLATED OR REF_CONSTRAINT_VIOLATED THEN
DBMS_OUTPUT.PUT_LINE('Constraint '||aCon.CONSTRAINT_NAME||' at Column '||aCon.COLUMN_NAME||' violated');
END;
END LOOP;
END;
It works with any check constraint (not only NOT NULL). Checking FOREIGN KEY Constraint should work as well.
Add/Modify/Delete of constraints does not require any further maintenance.
Does Postgres have any way to say ALTER TABLE foo ADD CONSTRAINT bar ... which will just ignore the command if the constraint already exists, so that it doesn't raise an error?
A possible solution is to simply use DROP IF EXISTS before creating the new constraint.
ALTER TABLE foo DROP CONSTRAINT IF EXISTS bar;
ALTER TABLE foo ADD CONSTRAINT bar ...;
Seems easier than trying to query information_schema or catalogs, but might be slow on huge tables since it always recreates the constraint.
Edit 2015-07-13:
Kev pointed out in his answer that my solution creates a short window when the constraint doesn't exist and is not being enforced. While this is true, you can avoid such a window quite easily by wrapping both statements in a transaction.
This might help, although it may be a bit of a dirty hack:
create or replace function create_constraint_if_not_exists (
t_name text, c_name text, constraint_sql text
)
returns void AS
$$
begin
-- Look for our constraint
if not exists (select constraint_name
from information_schema.constraint_column_usage
where table_name = t_name and constraint_name = c_name) then
execute constraint_sql;
end if;
end;
$$ language 'plpgsql'
Then call with:
SELECT create_constraint_if_not_exists(
'foo',
'bar',
'ALTER TABLE foo ADD CONSTRAINT bar CHECK (foobies < 100);')
Updated:
As per Webmut's answer below suggesting:
ALTER TABLE foo DROP CONSTRAINT IF EXISTS bar;
ALTER TABLE foo ADD CONSTRAINT bar ...;
That's probably fine in your development database, or where you know you can shut out the apps that depend on this database for a maintenance window.
But if this is a lively mission critical 24x7 production environment you don't really want to be dropping constraints willy nilly like this. Even for a few milliseconds there's a short window where you're no longer enforcing your constraint which may allow errant values to slip through. That may have unintended consequences leading to considerable business costs at some point down the road.
You can use an exception handler inside an anonymous DO block to catch the duplicate object error.
DO $$
BEGIN
BEGIN
ALTER TABLE foo ADD CONSTRAINT bar ... ;
EXCEPTION
WHEN duplicate_table THEN -- postgres raises duplicate_table at surprising times. Ex.: for UNIQUE constraints.
WHEN duplicate_object THEN
RAISE NOTICE 'Table constraint foo.bar already exists';
END;
END $$;
http://www.postgresql.org/docs/9.4/static/sql-do.html http://www.postgresql.org/docs/9.4/static/plpgsql-control-structures.html
http://www.postgresql.org/docs/9.4/static/errcodes-appendix.html
you can run query over pg_constraint table to find constraint exists or not.like:
SELECT 1 FROM pg_constraint WHERE conname = 'constraint_name'"
Creating constraints can be an expensive operation on a table containing lots of data so I recommend not dropping constraints only to immediately create them again immediately after - you only want to create that thing once.
I chose to solve this using an anonymous code block, very similar to Mike Stankavich, however unlike Mike (who catches an error) I first check to see if the constraint exists:
DO $$
BEGIN
IF NOT EXISTS ( SELECT constraint_schema
, constraint_name
FROM information_schema.check_constraints
WHERE constraint_schema = 'myschema'
AND constraint_name = 'myconstraintname'
)
THEN
ALTER TABLE myschema.mytable ADD CONSTRAINT myconstraintname CHECK (column <= 100);
END IF;
END$$;
Using information_schema.constraint_column_usage to check for the constraint doesn't work for foreign keys. I use pg_constraint to check for primary keys, foreign keys or unique constraints:
CREATE OR REPLACE FUNCTION add_constraint(t_name text, c_name text, constraint_sql text)
RETURNS void
AS $$
BEGIN
IF NOT EXISTS(
SELECT c.conname
FROM pg_constraint AS c
INNER JOIN pg_class AS t ON c.conrelid = t."oid"
WHERE t.relname = t_name AND c.conname = c_name
) THEN
EXECUTE 'ALTER TABLE ' || t_name || ' ADD CONSTRAINT ' || c_name || ' ' || constraint_sql;
END IF;
END;
$$
LANGUAGE plpgsql;
Examples:
SELECT add_constraint('client_grant_system_scopes', 'client_grant_system_scopes_pk', 'PRIMARY KEY (client_grants_id, tenant, "scope");');
SELECT add_constraint('client_grant_system_scopes', 'client_grant_system_scopes_fk', 'FOREIGN KEY (tenant,"scope") REFERENCES system_scope(tenant,"scope") ON DELETE CASCADE;');
SELECT add_constraint('jwt_assertion_issuers', 'jwt_assertion_issuers_issuer_key', 'UNIQUE (issuer);');
Take advantage of regclass to reduce verbosity, increase performance, and avoid errors related to table naming clashes between schemas:
DO $$ BEGIN
IF NOT EXISTS (SELECT FROM pg_constraint
WHERE conrelid = 'foo'::regclass AND conname = 'bar') THEN
ALTER TABLE foo ADD CONSTRAINT bar...;
END IF;
END $$;
This will also work for tables in other schemas, e.g.:
DO $$ BEGIN
IF NOT EXISTS (SELECT FROM pg_constraint
WHERE conrelid = 's.foo'::regclass AND conname = 'bar') THEN
ALTER TABLE s.foo ADD CONSTRAINT bar...;
END IF;
END $$;
In psql You can use metacommand \gexec for run generated query.
SELECT 'ALTER TABLE xx ADD CONSTRAINT abc' WHERE not EXISTS (SELECT True FROM pg_constraint WHERE conname = 'abc') \gexec
For me those solutions didn't work because the constraint was a primary key.
This one worked for me:
ALTER TABLE <table.name> DROP CONSTRAINT IF EXISTS <constraint.name> CASCADE;
Considering all the above mentioned answers , the below approach help if you just want to check if a constraint exist in the table in which you are trying to insert and raise a notice if there happens to be one
DO
$$ BEGIN
IF NOT EXISTS (select constraint_name
from information_schema.table_constraints
where table_schema='schame_name' and upper(table_name) =
upper('table_name') and upper(constraint_name) = upper('constraint_name'))
THEN
ALTER TABLE TABLE_NAME ADD CONSTRAINT CONTRAINT_NAME..... ;
ELSE raise NOTICE 'Constraint CONTRAINT_NAME already exists in Table TABLE_NAME';
END IF;
END
$$;
Don't know why so many lines of code ?
-- SELECT "Column1", "Column2", "Column3" , count(star) FROM dbo."MyTable" GROUP BY "Column1" , "Column2" , "Column3" HAVING count(*) > 1;
alter table dbo."MyTable" drop constraint if exists "MyConstraint_Name" ;
ALTER TABLE dbo."MyTable" ADD CONSTRAINT "MyConstraint_Name" UNIQUE("Column1", "Column3", "Column2");
I need to rename a constraint in an Oracle databse, but I don't know the old name at design-time.
What I would like to do is this:
declare
vOldName string;
begin
select CONSTRAINT_NAME
into vOldName
from user_constraints
where TABLE_NAME='AGREEMENT' and CONSTRAINT_TYPE='R';
alter table Agreement rename constraint vOldName to AGREEMENT_FK1;
end;
but I get the error message "PLS-00103: Encountered the symbol "ALTER" when expecting one of the following: begin case ".
How do I solve this problem?
Use dynamic PL/SQL:
declare
vOldName user_constraints.constraint_name%TYPE;
begin
select CONSTRAINT_NAME
into vOldName
from user_constraints
where TABLE_NAME='AGREEMENT' and CONSTRAINT_TYPE='R';
execute immediate 'alter table Agreement rename constraint '
|| vOldName || ' to AGREEMENT_FK1';
end;