Foreign Key Tutorial

Foreign Keys are the glue that holds a Database together.   This tutorial will show you how to easily manage your Foreign Keys using Database Schema Designer.

• Add / Edit a Foreign Key

  1. If Adding a new Foreign Key:

     There are a number of methods to create a new Foreign Key Constraint.   Choose the one you are most comfortable with:

     • Open Manage Foreign Keys screen and click the "Add" button.   See Manage Schema Objects Tutorial
     • Select "Insert -> Foreign Key" from the main menu.
       
     • Right Click the Schema and select "New -> Foreign Key -> Without selected Table" for a blank Foreign Key.
       
     • Right Click the Schema and select "New -> Foreign Key -> With selected Tables" for a Foreign Key populated with the selected Tables. **
       
     • Use the keyboard command "Ctrl+F" to add a blank Foreign Key.
     • Use the keyboard command "Ctrl+Shift+F" to add a Foreign Key populated with the selected Tables.**
     • You can also Auto-Add a Foreign Key using the selected Tables while creating a new Table.   See Add Table Tutorial to learn more.
     • ** If you are adding a Foreign Key with the selected Tables, the first selected Table will be the Child Table and the second will be the Parent Table.

     If Editing an existing Foreign Key:

     There are a number of methods to edit an existing Foreign Key Constraint.   Choose the one you are most comfortable with:

     • Open Manage Foreign Key screen and click the "Edit" button with the Foreign Key selected.   See Manage Schema Objects Tutorial
     • Double Click the Foreign Key in the main screen.
     • Right Click the Foreign Key in the main screen and select "Properties".
       
  2. Editing Foreign Key Properties
     • Select the Child Table.
       
     • Select the Parent Table.
       
     • ** The Child and Parent Table lists will only be available when adding a new Foreign Key to the Schema.   If you are editing an existing Foreign Key, these lists will be disabled.
     • Select the Primary Key or Unique Constraint that the Foreign Key will be based on.
       
     • Setup the Foreign Key Name as required.   See Object Names for more information.
     • The Constraint Columns will automatically be populated based on the Primary Key or Unique Constraint you chose earlier.
       
     • ** If the matching Column does not already exist in the Child Table it will be added.
     • If you wish to choose a different Child Table Column to constrain, Double Click that Column in the list to display the Select Substitute Column screen.
       
     • Toggle the "Update Cascade" or "Delete Cascade" checkboxes if you require these properties.
       
  3. Click OK to submit your changes.
     - OR -
     Click Cancel to discard your settings.
• Delete a Foreign Key

  There are a number of methods to delete a Foreign Key from the Schema.  Choose the one you are most comfortable with:

  • Open the Manage Foreign Keys screen and click Delete with the Foreign Key selected.   See Manage Schema Objects Tutorial
  • Open the Child Table's properties, select the Constraints Tab, select the Foreign Keys option, choose the Foreign Key in the list then press the Delete button.   See Edit Table Tutorial
  • Right Click the Foreign Key in the main screen and select Delete.
    
  • Delete the Foreign Key's Parent or Child Table.   See Delete Table Tutorial
• Formatting
  
  

  • Straightening Foreign Key Lines:

    Sometimes you may find that the process of moving and arranging your Schema can leave your Foreign Key Lines in a jumbled mess.   This is why we provided the straightening functionality.   When you straighten a Foreign Key you are allowing Database Schema Designer to re-create your Foreign Key Lines from End Point to End Point.   Doing so can quickly change your Schema from tangled to neat and clean.

    • On the main screen Click "Format -> Foreign Keys -> Staighten Lines -> All" to straighten all Foreign Key Lines in the Schema.
      
    • On the main screen Click "Format -> Foreign Keys -> Staighten Lines -> Selected" to straighten the Foreign Key Lines of the selected Tables.
      
    • Right Click a Table with a Foreign Key and choose "Straighten Foreign Key Lines".
      
    • Right Click the Foreign Key and choose "Straighten Foreign Key Lines".
      
    • Press and hold the Alt key then Double Click the Foreign Key.
  • Resetting Foreign Key End Points:

    Similar to the Straighten Foreign Key Lines functionality, resetting Foreign Key End Points can help to tame the maze that Foreign Keys can become.   Not only will the reset function straighten your lines, but it will also move your Parent and Child End Points to the shortest connection point possible.   The result is a Foreign Key that is easily followed by the eye from Parent to Child Table.

    • On the main screen Click "Format -> Foreign Keys -> Reset End Points -> All" to reset all Foreign Keys in the Schema.
      
    • On the main screen Click "Format -> Foreign Keys -> Reset End Points -> Selected" to reset the Foreign Key End Points of the selected Tables.
      
    • Right Click a Table with a Foreign Key and choose "Reset Foreign Key End Points".
      
    • Right Click the Foreign Key and choose "Reset Foreign Key End Points".
      
    • Press and hold Alt + Shift then Double Click the Foreign Key.
  • If the Foreign Key's End Points are either both vertical or both horizontal you can move the whole thing at one time.   Simply press and hold the Control while dragging the Foreign Key and both End Points and all of the Lines will move.
    

    Typically, the movement in this picture would require two operations: Move the Child End Point, then the Parent End Point.   It was done with one operation using the Control key while dragging.
  • When dragging a Foreign Key's End Points or Lines they will attempt to snap to the nearest intersection point.   To drag without snapping press and hold the Shift key.
  • You can also Reset or Straighten a Foreign Key while dragging its Tables.   See the Quick Tips to learn about  Object Manipulation.