Sybase 12.4.2 Creating primary and foreign keys, 125, To create a primary key in Sybase Central

CHAPTER 3 Working with Database Objects

Creating primary and foreign keys

Creating a primary key

The CREATE TABLE and ALTER TABLE statements allow many attributes of tables to be set, including column constraints and checks. This section shows how to set table attributes using the primary and foreign keys as an example.

The following statement creates the same skill table as before, except that a primary key is added:

CREATE TABLE skill	(
skill_id INTEGER	NOT NULL,
skill_name CHAR(	20 )	NOT NULL,
skill_type CHAR(	20 )	NOT NULL,
primary key( skill_id		)
)

The primary key values must be unique for each row in the table which, in this case, means that you cannot have more than one row with a given skill_id. Each row in a table is uniquely identified by its primary key.

Columns in the primary key are not allowed to contain NULL. You must specify NOT NULL on the column in the primary key.

Note Adaptive Server IQ does not enforce multi-column primary keys. You must specify the keyword UNENFORCED when you define a multi-column primary key.

Creating a primary key in Sybase Central

❖To create a primary key in Sybase Central:

1 Connect to the database.

2 Click the Tables folder for that database.

3 Right-click the table you wish to modify, and select Properties from the pop-up menu to display its property sheet.

4 Click the Columns tab, select the column name, and either click Add to Key or Remove from Key.

125