156 Part I EXAM PREPARATION Note from Table
156 Part I EXAM PREPARATION Note from Table 3.1 that most integrity techniques are applied before the data is actually allowed into the system, and therefore operate faster with a much lower overhead. Triggers offer the most functionality, but at a cost: the data is allowed into the system and then reacted upon. If a trigger determines that data should not be permitted, it must be rolled back. Use triggers sparingly and only when the application requires the additional functionality. When you define the table structure from the GUI, fill in the upper portion of the Design Table dialog box with column information by supplying the column name, selecting the appropriate data type from the drop-down list box, completing the Length field if the data type allows this to be adjusted, and setting whether the column is to allow NULL content. In the lower portion of the dialog box, you can optionally complete a description for the column, provide a default value, and, for numeric data types that allow for scale and precision, supply appropriate entries. If the column is to be an Identity column, select one of the integer data types, select Identity, and provide a starting value in the seed identification and an increment for the Identity. If the column is to be a row guid, select this option. If the column value is derived from a formula, specify the formula. WARNING Collation for an Individual Column A collation can be selected for an individual column but is not recommended because it causes great difficulty in the development of front-end applications. STEP BY STEP 3.7 Creating Tables, Indexes, and Constraints 1. Expand a server group, then the server, and then the database where the table is to be located. 2. Right-click Tables, and then select New Table. 3. Provide column definitions until all columns are defined. 4. Right-click on the column to be used as the Primary Key and select Set Primary Key. 5. In the top-left corner of the dialog box is a Table and Index Properties button that provides access to an area where you can provide further information to define the table. 6. Select the Relationships tab to define a Foreign Key. 7. Select the Indexes/Keys tab to define more indexing options.
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