Lesson 3: Setting a NOT NULL constraint on a column

Add a NOT NULL constraint to a column to prevent the column from allowing NULL values. By default, columns allow NULLs, but it is good practice to declare columns NOT NULL unless there is a reason to allow NULLs.

Prérequis

This lesson assumes that you have completed all preceding lessons. See Lesson 1: Creating a database file.

This lesson assumes that you have the roles and privileges listed in the Privileges section at the start of this tutorial: Tutorial: Creating a SQL Anywhere database.

Task

In the left pane of Sybase Central, double-click Tables.
Click Products, and then click the Columns tab in the right pane.
Click the ProductName column.
Click File » Properties.
Click the Constraints tab and click Values cannot be null.
Click OK.
Click File » Save.

Résultat

This constraint means that for each row added to the Products table, the ProductName column must have a value.

Suivant

Proceed to Lesson 4: Creating a foreign key.

Lesson 3: Setting a NOT NULL constraint on a column

Task

See also