i want to drop a column from composite primary key(not to delete from table). if my table is like this.
create table "scott"."xyz"(
"column1" not null,
"column2" not null,
"column3" not null,
"column4" not null,
"column5" not null,
"column6",
CONSTRAINT PRIMARY KEY ("column1","column2","column3","column4")
);
i want to alter this primary key to first three column without dropping it. beacuse i don't know CONSTRAINT name.
You don't need the constraint name:
ALTER TABLE "scott"."xyz" DROP PRIMARY KEY;
ALTER TABLE "scott"."xyz" ADD PRIMARY KEY ("column1","column2","column3");
But it is probably a good idea to give your PK a name in the future:
ALTER TABLE "scott"."xyz"
ADD CONSTRAINT pk_xyz PRIMARY KEY ("column1","column2","column3");
And I would not recommend to use quoted identifiers. You will have problems with various tools in the long run.
Related
I have seen the below create table statement :
create table cruise_orders
(cruise_order_id number,
order_date date,
constraint pk_or_id primary key (cruise_order_id,order_date));
so here the primary_key has two columns. But in case if I try the below statement and try to alter the table cruise_orders and add the column order_date to the primary key pk_or_id it throws an error saying "A table can have only one Primary key".
So how does it works with the first statement ? and why it doesn't work with the second alter statement ?
create table cruise_orders
(cruise_order_id number,
order_date date,
constraint pk_or_id primary key (cruise_order_id));
If you want it so that the cruise_order_id must be unique and, separately, that the order_date must be unique then use two constraints:
CREATE TABLE cruise_orders(
cruise_order_id NUMBER,
order_date DATE,
CONSTRAINT cruise_orders__or_id__pk PRIMARY KEY(cruise_order_id)
);
ALTER TABLE cruise_orders ADD CONSTRAINT cruise_orders__order_date__u UNIQUE(order_date);
If you really do want to have a single constraint with both columns the drop the first constraint and create a second with both columns:
CREATE TABLE cruise_orders(
cruise_order_id NUMBER,
order_date DATE,
CONSTRAINT cruise_orders__or_id__pk PRIMARY KEY(cruise_order_id)
);
ALTER TABLE cruise_orders DROP CONSTRAINT cruise_orders__or_id__pk;
ALTER TABLE cruise_orders ADD CONSTRAINT cruise_orders__coi__od__pk
PRIMARY KEY(cruise_order_id, order_date);
Then you will be able to have duplicate cruise_order_id values provided the order_date is different and vice-versa.
I am new to here, please help me to find an answer to the below query.
"How to add a primary key constraint on two columns to make a composite key column in a table?"
Instead of writing so many lines, kindly provide the answer as short as possible with code.
(I am creating a table in which I can have only one primary key on the values of two-columns as a composite key.)
JacknJill
You can create such constraint in scope of CREATE TABLE operator
CREATE TABLE foo (
id INTEGER,
name VARCHAR(25),
bar VARCHAR(255),
CONSTRAINT foo_pk PRIMARY KEY (id,name)
);
or ALTER TABLE operator
CREATE TABLE foo (
id INTEGER,
name VARCHAR(25),
bar VARCHAR(255)
);
ALTER TABLE foo ADD CONSTRAINT foo_pk PRIMARY KEY (id,name);
I use oracle and I try to have a recursive relation
CREATE TABLE "EVENT"
(
"EVENT_ID" NUMBER(18) NOT NULL, //primary key
"NAME" VARCHAR(20) NULL,
"RELATED_EVENT_ID" NUMBER(18) NULL //foreign key
);
Event 1 parent is Event 2....
When I try to create this table, I get this error.
ALTER TABLE "EVENT"
ADD CONSTRAINT "FK_RELATED_EVENT_ID"
FOREIGN KEY ("RELATED_EVENT_ID") REFERENCES "EVENT" ("RELATED_EVENT_ID")
Error report -
SQL Error: ORA-02270: no matching unique or primary key for this column-list
02270. 00000 - "no matching unique or primary key for this column-list"
*Cause: A REFERENCES clause in a CREATE/ALTER TABLE statement
gives a column-list for which there is no matching unique or primary
key constraint in the referenced table.
*Action: Find the correct column names using the ALL_CONS_COLUMNS
catalog view
You have two problems:
There is no primary key constraint on this table.
The foreign key constraint you defined has RELATED_EVENT_ID referencing RELATED_EVENT_ID. I suspect that was just a typo.
Change your table definition to:
CREATE TABLE EVENT
(EVENT_ID NUMBER
NOT NULL
CONSTRAINT PK_EVENT
PRIMARY KEY
USING INDEX,
NAME VARCHAR2(20),
RELATED_EVENT_ID NUMBER);
Then add the foreign key constraint as
ALTER TABLE EVENT
ADD CONSTRAINT EVENT_FK1
FOREIGN KEY (RELATED_EVENT_ID) REFERENCES EVENT(EVENT_ID);
db<>fiddle here
EDIT
Note that the better way to handle this is to use a junction table, such as:
CREATE TABLE EVENT_EVENT
(EVENT_ID1 NUMBER
CONSTRAINT EVENT_EVENT_FK1
REFERENCES EVENT(EVENT_ID),
EVENT_ID2 NUMBER
CONSTRAINT EVENT_EVENT_FK2
REFERENCES EVENT(EVENT_ID),
CONSTRAINT PK_EVENT_EVENT
PRIMARY KEY (EVENT_ID1, EVENT_ID2)
USING INDEX);
Then you can drop the RELATED_EVENT_ID column from EVENT as you no longer need it.
According to oracle document :
Foreign key specifies that the values in the column must correspond to values in a
referenced primary key or unique key column or that they are NULL.
In your case, create primary key on column (EVENT_ID) and use it in reference clause as following:
ALTER TABLE "EVENT"
ADD CONSTRAINT "FK_RELATED_EVENT_ID"
FOREIGN KEY ("RELATED_EVENT_ID")
REFERENCES "EVENT" ("EVENT_ID") -- this
Now, use EVENT2's EVENT_ID as RELATED_EVENT_ID in EVENT1 record to make EVENT2 as parent of EVENT1.
Cheers!!
Maybe I'm burnout, but I don't understand this. I have two tables in Oracle: TBL_a and TBL_x. I'm trying to create a foreign key between thos two tables as follows and get error
ORA-02270: no matching unique or primary key.
CREATE TABLE tbl_a (
cod_op integer,
cod_dni char(8),
cod_correl integer,
varchar2(50)
);
CREATE TABLE tbl_x (
cod_op integer,
cod_dni char(8),
blabla varchar2(50)
);
CREATE UNIQUE INDEX TBL_A_PK ON TBL_A (COD_OP);
CREATE UNIQUE INDEX TBL_x_PK ON TBL_x (COD_OP);
ALTER TABLE TBL_a ADD CONSTRAINT TBL_a_R01
FOREIGN KEY (COD_OP) REFERENCES TBL_x (COD_OP);
The problem is that you've created unique INDEXES on your tables, but you didn't create a unique or primary key CONSTRAINT. Oracle requires that the constraints exist in order to establish a foreign key relationship.
If you drop your existing indexes and add the appropriate constraints you can establish your foreign key relationship:
DROP INDEX TBL_A_PK;
DROP INDEX TBL_x_PK;
ALTER TABLE TBL_A
ADD CONSTRAINT UQ_A
UNIQUE(COD_OP)
USING INDEX;
ALTER TABLE TBL_X
ADD CONSTRAINT UQ_X
UNIQUE(COD_OP)
USING INDEX;
dbfiddle here
The table that is referred by the foreign key (here, tbl_x) must have a primary key or a unique constraint.
In your use case, as you are declaring a unique index on cod_op, you could simply make cod_op the primary key of tbl_x instead: that would make the error disappear.
Demo on DB Fiddle
In general, it is a good practice to have a primary key on any table. Extending the principe of turning your unique indexes to primary keys, your DDL statements could be simplified as follows:
CREATE TABLE tbl_x (
cod_op INTEGER PRIMARY KEY,
cod_dni CHAR(8),
blabla VARCHAR2(50)
);
CREATE TABLE tbl_a (
cod_op INTEGER PRIMARY KEY,
cod_dni CHAR(8),
cod_correl INTEGER,
blabla VARCHAR2(50),
CONSTRAINT TBL_a_R01 FOREIGN KEY (COD_OP) REFERENCES TBL_x (COD_OP)
);
Demo on DB Fiddle
How can I specify that a table has multiple columns that makeup the primary key? When I run this sql statement, I get "unknown data type "("
CREATE TABLE SH_LEAGUE_CONTACT_TEAM_ROLE(ROLE_NAME VARCHAR NOT NULL,
TEAM_ID INT NOT NULL,
CONTACT_ID INT NOT NULL,
FOREIGN_KEY(TEAM_ID) REFERENCES SH_LEAGUE_TEAM(ID),
FOREIGN_KEY(CONTACT_ID) REFERENCES SH_LEAGUE_CONTACT(ID),
PRIMARY KEY(ROLE_NAME, TEAM_ID, CONTACT_ID));
You have a typo in your statement, you have used FOREIGN_KEY (one word) instead of FOREIGN KEY (two words).