Access Building Table Relationships
Access for Office Access Access Access Access Access More. In a regular Access database, you create a table relationship using one of the When you create a relationship between tables, the common fields are not . Make any additional changes to the relationship, and then click OK. Relationships are links that associate a field in one table with a field in another. By linking the Student Name fields, you make sure that John in the Students. Access . relationships between your tables so that Access can bring related . If your table contains data, make a backup copy of the table before you .Creating a one to many relationship in a Access 2013 College Database
To see only tables, click Tables. Select one or more tables, and then click Add. After you have finished adding tables, click Close. Drag a field typically the primary key from one table to the common field the foreign key in the other table.
To drag multiple fields, press the Ctrl key, click each field, and then drag them. The Edit Relationships dialog box appears. Verify that the field names shown are the common fields for the relationship.
If a field name is incorrect, click on the field name and select the appropriate field from the list. To enforce referential integrity for this relationship, select the Enforce Referential Integrity box. When you are finished in the Relationships window, click Save to save your relationship layout changes. Access draws a relationship line between the two tables. If you selected the Enforce Referential Integrity check box, the line appears thicker at each end.
This means that the Indexed property for these fields should be set to Yes No Duplicates. If both fields have a unique index, Access creates a one-to-one relationship. Primary Keys Primary and foreign keys A primary key is the first field in each table of the database. You may recall that this field auto-numbers by default, so every record in the table has its own unique number to identify it. Access uses this number to quickly pull information together when you run queries or reports, which are covered later.
A foreign key is a field that is the primary field in its own table but that shows up in another table. These fields are the primary key in their own tables, but in the Orders table, they are considered foreign keys. Foreign Keys There are a few ways to establish relationships between tables: Using the Edit Relationships command located on the Design tab of the Ribbon Using the drag-and-drop method Both methods give you the same end result, but the drag-and-drop method is much easier and saves you several steps.
To relate tables with the drag-and-drop method: Select a field name from one table by holding down the left mouse button. Relationship Map Drag the field name from one table to the other table in the desired relationship. Drop the first field name onto the field name you want to relate by releasing the left mouse button.
How to define relationships between tables in an Access database
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. On the Tools menu, click Relationships. If you have not yet defined any relationships in your database, the Show Table dialog box is automatically displayed.
To create a relationship between a table and itself, add that table two times. Drag the field that you want to relate from one table to the related field in the other table. To drag multiple fields, press Ctrl, click each field, and then drag them. In most cases, you drag the primary key field this field is displayed in bold text from one table to a similar field this field frequently has the same name that is called the foreign key in the other table. Make sure that the field names that are displayed in the two columns are correct.
You can change the names if it is necessary.
Set the relationship options if it is necessary. These options will be explained in detail later in this article.
Click Create to create the relationship. Repeat steps 4 through 7 for each pair of tables that you want to relate. Whether you save the layout or do not save the layout, the relationships that you create are saved in the database. However, referential integrity is not enforced with queries. How to define a many-to-many relationship To create a many-to-many relationship, follow these steps: Create the two tables that will have a many-to-many relationship.
Create a third table. This is the junction table. In the junction table, add new fields that have the same definitions as the primary key fields from each table that you created in step 1. In the junction table, the primary key fields function as foreign keys.
Create, edit or delete a relationship - Access
You can add other fields to the junction table, just as you can to any other table. In the junction table, set the primary key to include the primary key fields from the other two tables. Note To create a primary key, follow these steps: Open a table in Design view.
Select the field or fields that you want to define as the primary key. To select one field, click the row selector for the desired field. To select multiple fields, hold down the Ctrl key, and then click the row selector for each field.
In Access or in Accessclick Primary Key on the toolbar. Define a one-to-many relationship between each primary table and the junction table. Referential integrity Referential integrity is a system of rules that Access uses to make sure that relationships between records in related tables are valid, and that you do not accidentally delete or change related data.
The matching field from the primary table is a primary key or has a unique index. The related fields have the same data type. There are two exceptions. Both tables belong to the same Access database.