The Columns tab is used to display and edit all the column information for a table. Using this tab, you can add, drop, and alter columns.

You can also use the column tab to change the name, data type, default value, and other properties of your table's columns.

Figure 7.3. The Columns Tab

To add a column simply click the Column Name field in an empty row and enter an appropriate value. Select a data type from the Datatype drop down list box . Check the check box under the NN column to disallow a null value and check the AI column if you are defining an autoincrement field.

Right clicking a row under the Column Name column opens a pop-up window with the following options:

To change the name, data type, default value, or comment of a column, double click on the value you wish to change. The content then becomes editable.

To modify the flags on a column (PRIMARY KEY, UNSIGNED, ZEROFILL) check the desired value in the Flags frame. Note that values only display in the flags frame when a column is selected.The ZEROFILL option only appears if the column type is numeric.

You can also add column comments to the Column Comment text area.

To the left of the column name is an icon that indicates whether the column is a member of the primary key. If the icon is a small key, that column belongs to the primary key, otherwise the icon is a blue diamond. To add or remove a column from the primary key, double click on the icon. You can also add a primary key by checking the PRIMARY KEY checkbox in the Column Details section of the table editor.