A unique constraint declares that the columns in the constraint must have unique values in the table. The Unique Constraints tab is only available for databases that support this constraint type. Select the foreign key in the list in the top section,.You can change the column order for the key with the Up and Down buttons. Check the Include checkbox for all columns in the column list that should be part of the foreign key and then select the corresponding column in the referenced table from the pull-down menu in the Referenced Column field.Use the Referenced Table controls to select the table that the foreign key refers to,.The Columns field is read-only and gets its value automatically when you select which columns to include in the key later, The pull-down lists include all actions that the database support, typically CASCADE, RESTRICT, NO ACTION and SET NULL. Select On Delete and On Update actions from the pull-down menus.Optionally enter a name for the foreign key in the first field in the list,.Click the Add button next to the list of foreign keys,.A list of all columns for the table being created/altered.Controls for selecting the table the currently selected foreign key refers to, including the database (catalog) and/or schema for the table,.Foreign keys are used by the database to enforce integrity, i.e., that there is a row in the referenced table with a primary key that matches the foreign key value when a new row is inserted or updated, and you can optionally declare rules for what to do when a referenced primary key is removed or updated in the referenced table. A foreign key is a column, or a combination of columns, that refer to the primary key of another table. In the Foreign Keys tab, you can declare one or more foreign keys for the table. Select the column(s) to be part of the primary key by clicking the checkboxes in the Include field in the columns list.Optionally enter a constraint name for the primary key constraint in the Constraint Name field,.A primary key is a column, or a combination of columns, that uniquely identifies a row in a table. The Primary Key tab contains information about an optional primary key for the table. To move a column to another location (Only supported for Create Table): If you don't enter a required attribute or enter an attribute that is unsupported for a data type, you will get an error message when you click Execute to create/alter the table.
For instance, there is no metadata available to tell if a data type requires, or allows, a size. The Create/Alter Table dialog uses database metadata to try to enable only the fields that apply to the selected data type, but please note that it is not always possible. The Auto Increment field, and possibly Start With and Increment By fields, are shown for numeric fields if the database supports automatically inserting the next available sequence number in a numeric column. In the last two fields, specify if the table is nullable and a default value to use for rows inserted into the table without specifying a value for the column.īelow the column list, you may find additional fields depending on the features supported by the database you are working with, and the data type for the current column. The Collation field is shown for character columns if the database supports the declaration of a collation for textual data.For others, like the decimal types, you can may specify both a size and a scale (the maximal number of decimals),
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