Access - Next steps with Access - Create a Relational Database
Learn what a relational database is and how to create one in Microsoft Access Access including Access 97, Access , Access , Access , Access , To create the relationship choose DataBase Tools > Relationships. To order the list so the query results appear in order by the date of the visit, click the . Access . relationships between your tables so that Access can bring related Ensure all the data in your database is relevant and kept up-to-date. Create relationships. .. Composite search criteria, more computed SQL, date comparison (page body who has Microsoft Office with MS-Word, also.
To enforce referential integrity for this relationship, select the Enforce Referential Integrity check box. For more information about referential integrity, see the Understanding Referential Integrity and the Enforce Referential Integrity sections.
The relationship line is drawn between the two tables. If you selected the Enforce Referential Integrity check box, the line appears thicker at each end. This means 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.
This means the Indexed property for this field should be set to Yes No Duplicates. The field on the "many" side should not have a unique index. When one field has a unique index and the other does not, Access creates a one-to-many relationship. Create a table relationship by using the Field List pane You can add a field to an existing table that is open in Datasheet view by dragging it from the Field List pane.
The Field List pane shows fields available in related tables and also fields available in other tables. 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 pane and the table to which you dragged the field.Microsoft Access 2007- Editing relationships
This relationship, created by Access, does not enforce referential integrity by default. To enforce referential integrity, you must edit the relationship.
See the section Change a table relationship for more information. Open a table in Datasheet view On the File tab, click Open. In the Open dialog box, select and open the database. In the Navigation Pane, right-click the table to which you want to add the field and create the relationship, and then click Open. The Field List pane appears. The Field List pane shows all of the other tables in your database, grouped into categories. When you work with a table in Datasheet view, Access displays fields in either of two categories in the Field List pane: Fields available in related tables and Fields available in other tables.
How to define relationships between tables in an Access database
The first category lists all of the tables that have a relationship with the table you are currently working with. 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 in position. The Lookup Wizard starts. 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.
Top of Page Delete a table relationship To remove a table relationship, you must delete the relationship line in the Relationships window. Carefully position the cursor so that it points at the relationship line, and then click the line. The relationship line appears thicker when it is selected. Note that when you remove a relationship, you also remove referential integrity support for that relationship, if it is enabled.
As a result, Access will no longer automatically prevent the creation of orphan records on the "many" side of a relationship. The Relationships window appears. 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. All tables that have relationships are displayed, showing relationship lines. Click the relationship line for the relationship that you want to delete. Access might display the message Are you sure you want to permanently delete the selected relationship from your database?.
If this confirmation message appears, click Yes.
MS Access - One-To-One Relationship
If either of the tables employed in the table relationship are in use, perhaps by another person or process, or in an open database object such as a formyou will not be able to delete the relationship. You must first close any open objects that use these tables before you can remove the relationship. Top of Page Change a table relationship You change a table relationship by selecting it in the Relationships window and then editing it.
Carefully position the cursor so that it points at the relationship line, and then click the line to select it. With the relationship line selected, double-click it or click Edit Relationships in the Tools group on the Design tab.
Click the relationship line for the relationship that you want to change. Double-click the relationship line. 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, the "Publishers" and "Titles" tables have a one-to-many relationship. That is, each publisher produces many titles.
Guide to table relationships - Access
But each title comes from only one publisher. A one-to-many relationship is created if only one of the related columns is a primary key or has a unique constraint. In the relationship window in Access, the primary key side of a one-to-many relationship is denoted by a number 1. The foreign key side of a relationship is denoted by an infinity symbol. Many-to-many relationships In a many-to-many relationship, a row in table A can have many matching rows in table B, and vice versa.
You create such a relationship by defining a third table that is called a junction table. The primary key of the junction table consists of the foreign keys from both table A and table B. For example, the "Authors" table and the "Titles" table have a many-to-many relationship that is defined by a one-to-many relationship from each of these tables to the "TitleAuthors" table.
One-to-one relationships In a one-to-one relationship, a row in table A can have no more than one matching row in table B, and vice versa. A one-to-one relationship is created if both of the related columns are primary keys or have unique constraints.
This kind of relationship is not common, because most information that is related in this manner would be in one table. You might use a one-to-one relationship to take the following actions: Divide a table with many columns. Isolate part of a table for security reasons. Store data that is short-lived and could be easily deleted by deleting the table. Store information that applies only to a subset of the main table. In Access, the primary key side of a one-to-one relationship is denoted by a key symbol.
The foreign key side is also denoted by a key symbol. How to define relationships between tables When you create a relationship between tables, the related fields do not have to have the same names. However, related fields must have the same data type unless the primary key field is an AutoNumber field.
You can match an AutoNumber field with a Number field only if the FieldSize property of both of the matching fields is the same. Even when both matching fields are Number fields, they must have the same FieldSize property setting.
How to define a one-to-many or one-to-one relationship To create a one-to-many or a one-to-one relationship, follow these steps: You cannot create or change relationships between open tables. In Access or Accessfollow these steps: Press F11 to switch to the Database window. 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.
When the Edit Relationships dialog appears click the Enforce Referential Integrity checkbox and Access will protect your data against you deleting or making changes to one table that will affect the data in the other table. Click Create to continue.
You can now close the dialog and answer Yes when prompted to save your changes. Entering data Now the tables have been created, you can enter your sample data. Enter this data into the Customer table: Below you will see short step-by-step walkthroughs showing you how to create a form to make it easier to enter data into your tables and also how to create a report containing the data from both tables. In addition to these, you'll also find plenty of use for Queries which allow you to extract information from the data you have stored.
Consider the situation where you want a list of the customers who visited your store and the date of these visits. To do this, from the Objects list choose Create tab and click Query Design.
In the Show Table dialog choose the Tables tab and select each table in turn and click Add and then Close.
Click the Run button it shows as an explanation mark and you'll see this list appear: When you click Run to run the query again, notice that this time the list appears in order by the date of the visit. To save this query so you can run it again at anytime, click its Close button and answer Yes when you're prompted to save the query. Type a name for it e. Customer details by date of visit and click OK. Totals and calculations in queries You can total results of a query.
For example you can total all the amounts spent by each customer for the month of September.