Creating Domains
A domain is a customized column definition that you use to create tables. When you create a table, you specify the characteristics of each column in the table. Often, across the tables in a database, there will be several columns that have the same characteristics. Rather than entering the same complex definition for each column, you can create a name for the collection of characteristics. This named set of column characteristics is called a domain. You can use this domain name in a column definition rather than typing out the full definition.
- Note:If you are going to use domains in your column definitions, you must create the domains before you use them in table definitions.
Column characteristics include:
- Datatype
- Default value: a literal value, NULL, or the name of the current user (USER)
- Nullability: NOT NULL prohibits NULL values in the column (columns are nullable by default)
- CHECK constraints: checks that the value being entered meets specified criteria
- Character set and optional collation order (output sort order for CHAR and VARCHAR columns)
- When you specify a column, only a column name and datatype are required. All other characteristics are optional.
Connecting to the TUTORIAL database
- If you are not already connected to the Tutorial database, in IBConsole, log on as the TUTOR user to the Local InterBase server.
- Select the Local Server in the left pane and then choose Server > Login to display the Server Login dialog.
- The user name TUTOR is already in the first field. Enter the password “tutor4ib” and click Login.
- To connect to the TUTORIAL database highlight the Tutorial.gdb icon in the left pane and choose Database > Connect.