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Create primary and foreign key with SQL

 
John King
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Hi,
I'm new to SQL. I need to create a table that
has a primary key to be used by a CMP entity
bean. I used following to create the table:
create table my_table(id not null number,
val_1 number, val_2 string)
ID is the primary key. Does above SQL statement requires id
to be unique? If not, what should I do to modify
the SQL statement? What should I do to add a
foregin key in above statement?
Thanks so much.
 
Sam Moran
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John, to create a Primary key you can use the ALTER command in your existing table by doing the following:
ALTER TABLE my_table ADD CONSTRAINT pk_id PRIMARY KEY (id)
If you are going to DROP the TABLE and start again use this:
CREATE TABLE my_table (
id NUMBER(10,0) NOT NULL,
val_1 NUMBER(4,0) NOT NULL,
val_2 VARCHAR(12) NOT NULL,

CONSTRAINT pk_id
PRIMARY KEY (id));
As far as the FORIEGN KEY is concerned you must reference another table.
Take a look at the following link for references and examples:
http://cisnet.baruch.cuny.edu/holowczak/classes/4300/week9.html
I hope this helps!
 
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