I've drop a constraint unique key with command:
ALTER TABLE table
DROP CONSTRAINT UNIQUE uk_nome;
it's removed because I don't see it, but when I try to re-add it with different parameter:
ALTER TABLE tale ADD CONSTRAINT UK_name UNIQUE (uk_1, uk_2);
I receive the error:
Errore SQL: ORA-00955: name is already used by an existing object.
Where is the problem?
You drop uk_nome and then add uk_name. I mean that there is a typo in uk_nome.
Resolved, the unique key is present, like index, into the system in the table dba_objects
Related
I came across an example with the following query
ALTER TABLE T ADD UNIQUE(col1)
Normally I would write
ALTER TABLE T ADD CONSTRAINT UNIQUE(col1)
ALTER TABLE T ADD CONSTRAINT UQ_1 UNIQUE(col1)
for unnamed and named constraint.
My question is whether the keyword CONSTRAINT is required ? I could not find reference on this. Can we write
ALTER TABLE T ADD FOREIGN KEY(col1) REFERENCE T1(col2)
ALTER TABLE T ADD PRIMARY KEY(col1)
Yes, we can use:
ALTER TABLE T ADD FOREIGN KEY(col1) REFERENCES T1(col2);
ALTER TABLE T ADD PRIMARY KEY(col1);
LiveDemo
or if you want to name them:
ALTER TABLE T ADD CONSTRAINT fk_T_T1 FOREIGN KEY(col1) REFERENCES T1(col2);
ALTER TABLE T ADD CONSTRAINT pk_T PRIMARY KEY(col1);
ALTER TABLE:
Image from: http://docs.oracle.com/cd/B28359_01/server.111/b28286/img/constraint_clauses.gif
and:
Image from: http://docs.oracle.com/cd/B19306_01/server.102/b14200/img/out_of_line_constraint.gif
As shown in the documentation (link below), the keyword CONSTRAINT is optional:
https://docs.oracle.com/cd/B28359_01/server.111/b28286/clauses002.htm#CJAEDFIB
However, it is required if you want to name your constraint.
The constraint <constraint_name> subclause is not required.
This is my exact query which is erroring out
alter table INDIL_MCAR drop constraint ABOB.INDI_MCAR_PK;
I m trying to remove the unique key constring from the table. It gives me the following error.
ORA-01735: invalid ALTER TABLE option
You can't prefix the constraint name... the table name yes, but not the constraint name. Remove the ABOB.:
alter table INDIL_MCAR drop constraint INDI_MCAR_PK;
I need to modify an existing PK. Therefore I drop an recreate it.
ALTER TABLE B DROP CONSTRAINT PK_B;
ALTER TABLE B ADD CONSTRAINT PK_B PRIMARY KEY ("TYP", "NR", "HH", "QUART");
Unfortunately the last Statement will give me an error ORA-00955
If I create the PK constraint like it was defined originally with:
ALTER TABLE B ADD CONSTRAINT PK_B PRIMARY KEY ("TYP", "NR", "HH");
everything works fine.
Perhaps there is an INDEX associated with the PRIMARY KEY CONSTRAINT, and it is also named as PK_B.
You can check it as :
SELECT * FROM USER_INDEXES WHERE TABLE_NAME='<table_name>';
If that's true, then do :
ALTER INDEX "PK_B" RENAME TO "PK_XYZ";
Update : Regarding ALTER INDEX statement, few important points as mentioned by Justin in the comments
Oracle implicitly creates an UNIQUE index to support the PRIMARY KEY CONSTRAINT. Since, the index is of the same name that of the primary key, and now that the primary key is being modified, it is better to drop and re-create the index again as per the definition of the old primary key.
My conclusion :
The primary key constraint is enforced through a unique index.
If Oracle already finds an index – unique or non-unique – it uses it
for the primary key.
If the index was initially created as non-unique, it will continue to
show as non-unique, however it will actually be a unique index.
A good demonstration and quite detailed on other aspects too, by Arup : Primary Keys Guarantee Uniqueness? Think Again.
I had the same issue where I had to do the following to delete reference to a table from the view whilst recreating the database from the scratch. I was searching for the same in tables and indexes first.
connect sys/oracle as sysdba;
select * from all_tables
select * from all_indexes
(finally located the reference in the views)
select * from all_views where view_name like '%WKSTSTATE%';
drop view RUEGEN.WKSTSTATE;
I'm working on H2 database, and I meet this problem -
to drop one constraint is fine, I can use this statement
alter table customer drop constraint if exists fk_customer_order ;
for add one constraint is fine too, I can use this statement.
alter table customer add constraint fk_customer_order foreign key (order_id) references order (id) on delete cascade on update cascade;
but the problems is, in customer table I have more foreign key and I want delete them in one query statement.
Something like this
alter table customer drop constraint fk_customer_order
drop constraint fk_customer_information
drop constraint ....
but this seem can not be done in h2 database, anyone can tell me can or not add or drop multi constraint by 1 sql statment? Any answer are welcome and I appreciate much.
I think it can not be done. Why don't you use multiple statements?
I'm trying to create a constraint on the OE.PRODUCT_INFORMATION table which is delivered with Oracle 11g R2.
The constraint should make the PRODUCT_NAME unique.
I've tried it with the following statement:
ALTER TABLE PRODUCT_INFORMATION
ADD CONSTRAINT PRINF_NAME_UNIQUE UNIQUE (PRODUCT_NAME);
The problem is, that in the OE.PRODUCT_INFORMATION there are already product names which currently exist more than twice.
Executing the code above throws the following error:
an alter table validating constraint failed because the table has
duplicate key values.
Is there a possibility that a new created constraint won't be used on existing table data?
I've already tried the DISABLED keyword. But when I enable the constraint then I receive the same error message.
You can certainly create a constraint which will validate any newly inserted or updated records, but which will not be validated against old existing data, using the NOVALIDATE keyword, e.g.:
ALTER TABLE PRODUCT_INFORMATION
ADD CONSTRAINT PRINF_NAME_UNIQUE UNIQUE (PRODUCT_NAME)
NOVALIDATE;
If there is no index on the column, this command will create a non-unique index on the column.
If you are looking to enforce some sort of uniqueness for all future entries whilst keeping your current duplicates you cannot use a UNIQUE constraint.
You could use a trigger on the table to check the value to be inserted against the current table values and if it already exists, prevent the insert.
http://download.oracle.com/docs/cd/B19306_01/appdev.102/b14251/adfns_triggers.htm
or you could just remove the duplicate values and then enfoce your UNIQUE constraint.
EDIT: After Jonearles and Jeffrey Kemp's comments, I'll add that you can actually enable a unique constraint on a table with duplicate values present using the NOVALIDATE clause but you'd not be able to have a unique index on that constrained column.
See Tom Kyte's explanation here.
However, I would still worry about how obvious the intent was to future people who have to support the database. From a support perspective, it'd be more obvious to either remove the duplicates or use the trigger to make your intent clear.
YMMV
You can use deferrable .
ALTER TABLE PRODUCT_INFORMATION
ADD CONSTRAINT PRINF_NAME_UNIQUE UNIQUE (PRODUCT_NAME)
deferrable initially deferred NOVALIDATE;