Create, edit or delete a relationship - Access
This tutorial explains how to create a one-to-many relationship in Microsoft Access In order to create the relationship you first need two tables. I assume. Access doesn't directly support a many-to-many relationship, so you must create a third table: an "associate table." It contains a primary key and. going to take a look at the One to Many Relationship in Access this should put you on the right track to penetrating the meaning of.
Because we are going to create a relationship between the customer table and the orders table, all orders for individual customers will be connected with the correct persons' customer details. This is made possible by connecting the primary key field of the customer table with the corresponding foreign key field in the orders table.
If you remember, Primary and Foreign Keys were covered in my last blog post. The first step is to create a new Access Database. Lets call it Customer Orders. CustomerId is going to be the foreign field when we create the relationship. We are now going to select which tables are going to be used in the relationship. There are just two tables in our example database.
- Create a one-to-many relationship in Access
- Accommodating a many-to-many relationship in Access
- Create, edit or delete a relationship
Click on tblCustomer to highlight it in blue if it is not highlighted already. You will notice in the diagram below that each box has it's fields listed and primary keys indicated. Notice the mouse pointer image changes from a circle with a line across to a plus sign as it hovers over the fields in tblOrder. The Edit Relationships dialog box appears.
This option is explained in detail below. Access allows for several different types of relationships. One-to-One One-to-Many Many-to-Many The relationship type you will come across most frequently—and the one created in our bookstore scenario—is the One-to-Many relationship.
One-to-Many The One-to-Many relationship means data for that field will show up a single time in one table but many times in the related table.
For example, let's look at one of the book titles in our bookstore. The Book ID for the book should appear only once in the Books table because this table lists every title stocked in the store.
Microsoft Access Tips: The One to Many Relationship
But it will probably appear many times in the Orders table because we hope it gets ordered by many people many times. The symbols for the One-to-Many relationship look like this: You should click Enforce Referential Integrity to make sure you never have an order for a book that doesn't appear in the Books table.
Selecting this option tells Access to check for these things when someone is working with your data records. Editing existing relationships Access allows you to edit relationships that already exist. This can be done using the Edit Relationships command on the Ribbon. However, a much simpler way is to simply double-click the link that appears in the relationship map.
Either method brings up the Edit Relationships dialog box, where you can change your settings. If you haven't already done so, save the sample Ready2Read database to your computer. The first category lists all of the tables that have a relationship with the table with which you are currently working.
The second category lists all of the tables with which your table does not have a relationship. To add a field to your table, drag the field that you want from the Field List pane to the table in Datasheet view. Drag the field that you want from the Field List pane to the table that is open in Datasheet view. When the insertion line appears, drop the field into position.
The Lookup Wizard starts.
Create a relationship
Follow the instructions to complete the Lookup Wizard. The field appears in the table in Datasheet view. When you drag a field from an "other" unrelated table and then complete the Lookup Wizard, a new one-to-many relationship is automatically created between the table in the Field List and the table to which you dragged the field.
Edit a relationship You change a relationship by selecting it in the Relationships window and then editing it. Carefully position the cursor so that it points to the relationship line, and then click the line to select it. The relationship line appears thicker when it is selected.
With the relationship line selected, double-click it. The Relationships window appears.
Create a one-to-many relationship in Access
If you have not yet defined any relationships and this is the first time you are opening the Relationships window, the Show Table dialog box appears. If the dialog box appears, click Close. On the Design tab, in the Relationships group, click All Relationships. All tables with relationships are displayed, showing relationship lines. Note that hidden tables tables for which the Hidden check box in the table's Properties dialog box is selected and their relationships will not be shown unless Show Hidden Objects is selected in the Navigation Options dialog box.
Click the relationship line for the relationship that you want to change. Double-click the relationship line. On the Design tab, in the Tools group, click Edit Relationships. Make your changes, and then click OK. The Edit Relationships dialog box allows you to change a table relationship.
Specifically, you can change the tables or queries on either side of the relationship, or the fields on either side.
You can also set the join type, or enforce referential integrity and choose a cascade option. For more information about the join type and how to set it, see the section Set the join type.
For more information about how to enforce referential integrity and choose a cascade option, see the section Enforce referential integrity. Set the join type When you define a table relationship, the facts about the relationship inform your query designs. For example, if you define a relationship between two tables, and you then create a query that employs the two tables, Access automatically selects the default matching fields based upon the fields specified in the relationship.