Foreign Keys

Zequel lets you view, create, and drop foreign key constraints through the TableStructure panel.

Viewing Foreign Keys

Switch to the Foreign Keys tab in the TableStructure panel. Each foreign key displays:

Field	Description
Name	The constraint name, shown with a link icon.
Column	The source column in the current table.
References	The referenced table and column, shown as table.column.
On Update	The referential action on update (e.g. NO ACTION, CASCADE).
On Delete	The referential action on delete (e.g. NO ACTION, CASCADE, SET NULL).

If the table has no foreign keys, a "No foreign keys found" message is shown.

Creating a Foreign Key

Click the Add Foreign Key button at the top of the Foreign Keys tab to open the ForeignKeyEditorDialog.

Fields

• Constraint Name -- A name for the foreign key. An auto-generated name is suggested based on the source table, columns, and referenced table (e.g. fk_orders_user_id_users). You can override it.
• Source Columns -- Click columns from the current table to select them as source columns. Selected columns appear as chips above the column list. Click the remove button on a chip to deselect.
• Referenced Table -- Select the target table from a dropdown. The list shows all tables in the current database.
• Referenced Columns -- After selecting a referenced table, its columns are loaded. Click columns to map them to the source columns in order. The dialog shows the mapping (e.g. user_id -> id). The number of referenced columns must match the number of source columns.
• ON UPDATE -- The action to take when the referenced row is updated. Options: NO ACTION, CASCADE, SET NULL, SET DEFAULT, RESTRICT.
• ON DELETE -- The action to take when the referenced row is deleted. Same options as ON UPDATE.

SQL Preview

Click Show SQL Preview to see the generated statement, for example:

ALTER TABLE "orders" ADD CONSTRAINT "fk_orders_user_id_users"
  FOREIGN KEY ("user_id")
  REFERENCES "users" ("id")
  ON UPDATE NO ACTION
  ON DELETE CASCADE

Click Add Foreign Key to execute. The button is disabled until all required fields are filled and the source/referenced column counts match.

Dropping a Foreign Key

Click the Drop icon next to a foreign key. A ConfirmDeleteDialog appears with:

• A warning that the action cannot be undone.
• The SQL statement (e.g. ALTER TABLE "orders" DROP CONSTRAINT "fk_orders_user_id_users").
• A confirmation checkbox.

After confirming, the constraint is dropped and the view refreshes.

Next Steps

• Managing columns
• Managing indexes
• Table info and DDL