Key Definition (key_definition)
A key definition in a
CREATE TABLE statement or an ALTER TABLE statement defines the key in a base table. The key definition is introduced by the keywords PRIMARY KEY.Syntax
<key_definition> :: PRIMARY KEY (<column_name>,...)
column_nameSQL statement for creating a
person table with a one-column primary key for the column cno:CREATE TABLE person (cno FIXED(4), firstname CHAR(7), name CHAR(7), account FIXED(7,2), PRIMARY KEY (cno))
Rows are inserted in the same way as in a base table without a key definition. Double entries for the customer number, however, are rejected.
Explanation
The column name must identify a column in the base table. The specified column names are key columns in the table.
A key column must not identify a column of the data type
LONG and is always a NOT NULL column. The database system ensures that no key column has a NULL value and that no two rows of the table have the same values in all key columns.See also:
Restrictions