I need a column which should store more than 4000 characters(to be exact: between 4000 to 8000). And I want that particular column to be a primary key. Since I have dependency in UI end for that particular column to be primary key.
I tried CLOB and varchar(max) but those datatypes doesn't allow primary key property.
Can anyone help me with a proper datatype which can satisfy both conditions?
I'm using Oracle SQL developer 18.3.0.277
You cannot specify a primary key or unique constraint on a CLOB column. If you try then you get the exception:
ORA-02329: column of datatype LOB cannot be unique or a primary key
You can have a composite primary key with two VARCHAR2(4000) columns:
CREATE TABLE table_name (
value_start VARCHAR2(4000),
value_end VARCHAR2(4000),
CONSTRAINT table_name__value__pk PRIMARY KEY (value_start, value_end)
);
Or, from Oracle 12, you can set the system setting MAX_STRING_SIZE to be extended and can use:
CREATE TABLE table_name (
value_start VARCHAR2(8000) PRIMARY KEY
);
However
I would question the design choice of using a VARCHAR2(8000) column as a primary key as you will need to duplicate the (large) column value in all the referential constraints. Instead, make the value UNIQUE and provide a IDENTITY column which can act as the primary key with a one-to-one correspondence to the large string values.
Related
1.In which order should we apply primary key, foreign key constraints and create index if the Oracle table has millions of data and does not have prior constraints?
2.Can we use 'NOLOGGING PARALLEL' while applying primary key and foreign key constraints like we do while applying(creating) indexes? Or any other method so that primary key and foreign key constraints could be applied faster?
Note: I'll use bullets so that it is easier to read, as it is easy to get lost in long sentences.
My thoughts on the subject; see if anything of this helps.
Well,
as you can't create a foreign key constraint if column(s) it references aren't part of primary or unique key
you'll obviously first have to create primary key constraints
and then foreign key constraints
When you
create a primary key constraint,
Oracle automatically creates index that supports it, unless there's already an index you can use (with the USING INDEX clause)
which means that you can "skip" some indexes (those for primary key constraints as they'll already exist) and virtually save some time
and create "other" indexes
On the other hand,
if you first create unique index on future primary key columns and
later add primary key constraint with the USING INDEX clause, Oracle will "skip" check for possible duplicate values because unique index won't allow them
The same goes for
NOT NULL constraint on future primary key columns; primary key doesn't allow NULLs so - if a column already is NOT NULL, enforcing primary key constraint can skip NULL check as well
I don't know
which columns you'll additionally index, but - as you're on Oracle 11g -
don't forget to index all foreign key constraint columns
because you might encounter unexpected table locks if you
update primary key column in parent table, or
delete parent record
Can you do it with no logging and in parallel? Yes:
SQL> create table test (id number, name varchar2(20));
Table created.
SQL> create unique index ui1_test_id on test (id) nologging parallel 20;
Index created.
SQL> alter table test add constraint pk_test primary key (id) using index ui1_test_id nologging parallel 20;
Table altered.
SQL>
But you'll probably want to change the index and table back to NOPARALLEL and LOGGING when the initial creation is done.
SQL> alter index ui1_test_id noparallel;
Index altered.
SQL> alter table test logging noparallel;
Table altered.
I'm using pl sql developer 12.what i want is to add the make the primary key sequential using oracle 12' windows and forms , not by scripting. I can't find out how?.
aslo, how can i make one to one relation between 2 tables (user,role), in user table i added role_id as foreign key; but the relation seem one to many!!!
In Oracle 12c and above, you define that column as identity columns:
CREATE TABLE mytable (
id NUMBER GENERATED ALWAYS AS IDENTITY,
-- other columns ...
);
A #Mureinik already said, in Oracle 12 and higher versions you can define your primary key column as NUMBER GENERATED ALWAYS AS IDENTITY to get a unique sequential value.
To enforce a one-to-one relationship in the database you'd want to have your ROLE_ID column defined as a primary key on one table, and as either a UNIQUE or PRIMARY key on the second table, with a foreign key relationship between the tables. In other words:
CREATE TABLE T1 (ROLE_ID NUMBER
CONSTRAINT PK_T1
PRIMARY KEY
...);
CREATE TABLE T2 (ID_T2 NUMBER
PRIMARY KEY,
ROLE_ID NUMBER
CONSTRAINT T2_U1
UNIQUE
CONSTRAINT T2_FK1
REFERENCES T1(ROLE_ID)
ON DELETE CASCADE,
...);
After the above ROLE_ID will be the primary key on T1, a unique key on T2, and T2.ROLE_ID will be a foreign key to T1.
Best of luck.
what I have done lastly is that i downloaded sql developer 64 w, and from it; I connected with the database then I made the column sequential
There is a requirement in our application to create the unique primary key which depend on the value of another unique column (ERROR_CODE). But our application is in a geo active active environment (have several active databases which are synchronized using another program).
Therefore even-though we have a unique constraint on this ERROR_CODE field, there is a possibility that each database has a row with a different PK for the same ERROR_CODE. During the database synchronization, this is a problem, because there are some child tables which has the PK stored in one DB and other rows contain the PK stored in other DB. Because of the unique constraint of ERROR_CODE, sync process cannot move both rows to each database (which is also not a good thing to do).
So there is a suggestion to use the hash of the ERROR_CODE field as the PK value.
I would like to know whether we can define a function based Primary key in oracle?
If PK field is "ID",
"ID" should be equal to ora_has(ERROR_CODE).
Is it possible to define the primary key like that in oracle?
In Oracle 10 you cannot do this, but in Oracle 11 you can. You have to create a virtual column, such columns can be used also as primary key:
ALTER TABLE MY_TABLE ADD (ID NUMBER GENERATED ALWAYS AS (ora_has(ERROR_CODE)) VIRTUAL);
ALTER TABLE MY_TABLE ADD CONSTRAINT t_test_pk PRIMARY KEY (ID) USING INDEX;
Not able to create /find the logic to apply FK on a column in child table referencing a column from composite PK of parent table.
create table product(prod_id number,
prod_name varchar2(20),
price number,
constraint PK12 primary key(prod_id,prod_name));
Table created.
create table purchase(prod_id number,
purchase_price number,
constraint FK12 foreign key(prod_id) references product(prod_id));
create table purchase(prod_id number,
purchase_price number,
constraint FK12 foreign key(prod_id) references product(prod_id))
ERROR at line 1:
ORA-02270: no matching unique or primary key for this column-list
Kinldy suggest how i can incorporate this logic.
Thanks.
You can't.
As the error says there's no matching primary key for that column list; you must have one. You have three options:
Remove PROD_NAME from the primary key of PRODUCT. On the face of it this seems like the logical solution, if this is not required in order to make the primary key unique.
Add PROD_NAME to the PURCHASE table.
Create a unique index on PURCHASE.PROD_ID. This seems excessive if it would be a primary key candidate anyway.
I suspect that this is not unique to Oracle. Considering you have a composite primary key in the referenced table, that implies that only one of the columns comprising the composite key is not enough to uniquely identify the record in that table. Therefore, it's impossible to reference only a single column of the primary key in a foreign key relationship that's one-to-many (e.g. one record in the referenced table can have many records in the referencing table--the one with the FK). However, if the relationship to be established is many-to-many, this may be possible.
HTH.
The semantic of our data is case insensitive, so we configure the oracle sessions to be case insensitive:
alter session set NLS_COMP=LINGUISTIC;
alter session set NLS_SORT=BINARY_AI;
Then, to take advantage of indexes we would also want the primary key to be case insensitive as well:
create table SCHEMA_PROPERTY (
NAME nvarchar2(64) not null,
VALUE nvarchar2(1024),
constraint SP_PK primary key (nlssort(NAME))
)
However, this runs into "ORA-00904: : invalid identifier", so I assume it is not possible to use the nlssort() function in the PK definition.
Next attempt was to associate a case-insensitive unique index to the primary key:
create table SCHEMA_PROPERTY (
NAME nvarchar2(64) primary key using index (
create unique index SP_UQ on SCHEMA_PROPERTY(nlssort(NAME))),
VALUE nvarchar2(1024)
);
but this failed too:
Error: ORA-14196: Specified index cannot be used to enforce the constraint.
14196. 00000 - "Specified index cannot be used to enforce the constraint."
*Cause: The index specified to enforce the constraint is unsuitable
for the purpose.
*Action: Specify a suitable index or allow one to be built automatically.
Should I just conclude that Oracle does not support case-insensitive semantics for a PK constraint? This works fine in MSSQL which has a simpler approach in dealing with collations.
We could, of course, create a unique index instead of the primary key, but I wanted to make sure first that the normal way to do this is not supported.
Our oracle version is 11.2.0.1.
As you are on 11.2 you can use a virtual column to achieve this:
CREATE TABLE SCHEMA_PROPERTY (
REAL_NAME nvarchar2(64) not null,
NAME generated always as (lower(real_name)) primary key,
VALUE nvarchar2(1024)
);
Create a unique index to enforce case-insensitive PK:
create table SCHEMA_PROPERTY (
NAME nvarchar2(64),
VALUE nvarchar2(1024),
constraint SP_PK primary key (NAME)
);
create unique index SP_UN on SCHEMA_PROPERTY(lower(NAME));