Microsoft Access 2010

Transcription

1 Microsoft Access 2010 This class is designed to cover the following basics: Identify the components of the Access 2010 environment Identify the components of a database Organize data in tables View data in tables Query a database Design forms Generate reports Introduction Access is a relational database, i.e. an information structure that stores data in twodimensional tables that can be linked to each other for cross-referencing. Relational databases store information about one topic (also called an entity ) in each table. Using Access to build a relational database lets you extract data from multiple tables, or reorganize and display data contained in the tables in a meaningful way. The tables themselves are not modified or altered by extracting data or running a query. Relationships among tables can be: One-to-One (rarely used) One-to-Many Many-to-Many (need to define a new table) A One-to-Many relationship is the most common type of relationship. In this type of relationship, a row in table A can have many matching rows in table B, but a row in table B can have only one matching row in table A. An example would be a table that presents Customer Information and one that presents Customer Purchases. You have a one-tomany relationship between Customer and Customer Purchases. Each customer can produce many purchases, but each purchase is made by only one customer. In this example, the Customer Information table is considered the Parent Table while the Customer Purchases table is considered the Child Table. Database Objects you will find in Access 2010 include: Table (tbl): The object in which the data resides. Query (qry): A command that is run to extract or retrieve data from one or multiple tables. Form (frm): A graphical interface used for data input. Although the data might will end up in a Table, the user may not see the table at all if they interface with a Form to input data. Forms can also be used to display data. Report (rpt): A report displays information from a query or from a table. It can be displayed on a screen, or printed to paper/pdf. Tables A table is a grid that stores information in a database similar to the way an Excel worksheet stores information in a workbook. A table should contain information on only one topic, and ideally the same information should not appear in more than one table. Access Handout Page 1 Spring 2011

2 This increases efficiency and reduces the risk of data-entry errors. Data is organized into fields (columns) and records (rows). A field is a specific category of data in a table. Each field appears as a column in the table and should relate directly to the topic of the table. A record is a collection of data about one item in a table. Each record appears as a row in the table. A primary key is a field that uniquely identifies each record in a table (e.g. an ID number). A primary key is highly recommended although a primary key is not required. A primary key matches records from one or more tables with records in another table, cross-referencing related information. A primary key can be automatically set by Microsoft Access or can be identified by the user. A composite key is a primary key that is made from more than one field. For example, an Order Details table that stores line items for orders might use two fields in its primary key: Order ID and Product ID. A foreign key is a field in a related table (child table) that completes a relationship by identifying the parent table. Referential integrity is a database concept that ensures that relationships between tables remain consistent. When one table has a foreign key linked to another table, the concept of referential integrity states that you may not add a record to the table that contains the foreign key unless there is a corresponding record in the linked table. Normalization is the process of organizing your data and breaking it into smaller tables that are easier to manage. The primary reason we normalize a database is to prevent redundant data. Queries A query is a way to view, change and analyze data. Queries are the primary mechanism for retrieving information from a database. Queries consist of questions presented to the database in a predefined format. You can use a query to filter and sort particular data from one table or multiple tables to find specific information. Queries can be used as the source of records for forms and for reports. Forms A form provides a quick and easy way to view, create and modify records in your database. You can also use a form to provide access to other forms and reports, and to provide dialog boxes that can be used to perform specific tasks. Forms can be based on a table or a query. Data is never stored in forms; a form only displays the data stored in a table. Reports A report is a professional and efficient way to present data in a printed format. You can calculate totals, categorize records and view totals in a chart. Access Handout Page 2 Spring 2011

3 Additional Access Objects The four most common objects in Access are the four mentioned above: Tables, Queries, Forms and Reports. In addition, there are a few additional, less-common objects: Pages: These can be used to enter or display data via the Internet. Pages are stored as HTML files, with data read from and written to the database. Macros: You can write a macro for your own functions and programs. Module: A module can be used like a macro where you can write your own functions and programs. Everything that can be done in a macro can also be done in a module, but you don't get the Macro interface that prompts you for what is needed for each action. Modules are far more powerful, and are essential if you plan to write code for a multi-user environment, since macros do not include error handling. Most serious Access users start out with macros to get a feel for things, but end up using modules almost exclusively. Good-Practice Naming Conventions Table tbl_employee Form frm_employee Query qry_employee Report rpt_employee Overview of Steps to Create a Database in Access When creating an Access database, you ll follow the list of steps below: 1. Map out (usually on a piece of paper) the different Tables, Fields and Relationships that will comprise the database. 2. Create those Tables in Access (this means creating e.g. the tables, fields and primary keys). 3. Link/Relate the Tables together by creating relationships between them. 4. Create Queries to collate, retrieve and view data from multiple Tables. 5. Create Forms that can be used to efficiently enter and edit data in Tables. 6. Create Reports to summarize the data and present it in a concise way. Creating Tables 1. Select Create/Table Design to create a new Table. 2. Under the Field Name column, enter the fields of your Table. 3. Under Data Type column, enter the type of data you want for each field. Data type is the attribute of a variable or field that determines what kind of data it can hold. For example, in a Microsoft Access database, the Text and Memo field data types allow the field to store either text or numbers, but the Number data type will allow the field to store numbers only. You need to use number types for calculation. Use the Currency data type to display or calculate currency values. Other data types are Date/Time, Yes/No, Auto Number, and OLE object (Picture). 4. Under the Description column, enter a description of what the field is. (This field is optional). Access Handout Page 3 Spring 2011

4 5. Define a Primary Key by selecting the row(s) of the field(s) you d like to designate as the Primary Key and clicking on Primary Key on the Design tab in the Tools group. 6. Save the table by clicking on the Save icon from the Quick Access Toolbar. A Save As dialog box will appear and you can type the desired name for your Table in the Table Name text box. Then click OK. Switching Views To switch views, simply click the View button from the Home Ribbon and select Database View/Design View. Database View: Displays the view, which allows you to enter raw data into your database table. Design View: Displays the view, which allows you to enter fields, data-types, and descriptions into your database table. Entering Data A Table is one way you can enter or modify data. In the Navigation Pane, double-click the desired Table. (You will be in Design View.) Select the desired Field and enter the appropriate data into the Field. Press either the Enter or Tab key after each entry to move to the next cell. You do not need to save the information; it is saved automatically. Note that there is an Undo icon on the Quick Access Toolbar. The Record Navigation Bar The Record Navigation Bar in the Datasheet View lets you navigate between records. You can use the arrows to go to the Next, Previous, First or Last Record in the Recordset. You can also add a New Record by clicking on the arrow with the yellow star next to it. You can also use the Search text box and put in specific words or numbers that might exist as data which has been entered into a record set. Clicking the Filter button can remove a filter which has been applied to a Table. Creating Relationships between Tables 1. On the Database Tools tab, in the Relationships group, click Relationships. 2. If you have not yet defined any relationships, the Show Table dialog box automatically appears. If it does not appear, on the Design tab, in the Relationships group, click Show Table. 3. In the Show Table dialog box, on the Tables tab, select the desired Tables. 4. Click Add to add the selected Tables to the Relationships window and Close the Show Table dialog box when finished. 5. 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 Access Handout Page 4 Spring 2011

5 appears: 6. 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. 7. To enforce Referential Integrity for this relationship, select the Enforce Referential Integrity check box. 8. Click Create. 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. In addition, again only if you selected the Enforce Referential Integrity check box, the number 1 appears over the thick portion on one side of the relationship line, and the infinity symbol ( ) appears over the thick portion on the on the other side of the line, as shown in the following figure: Referential Integrity prevents orphan records and keeps references in sync. It is a restriction on data that in two related Tables, an entry will not be allowed in the child Access Handout Page 5 Spring 2011

6 Table unless the entity already exists in the parent Table. Suppose you have a one-tomany relationship between Shippers and Orders and you want to delete a Shipper. If the shipper you want to delete has orders in the Orders Table, those orders will become "orphans" when you delete the Shipper record. The orders will still contain a shipper ID, but the ID will no longer be valid, because the record that it references no longer exists. The order would therefore become an orphan record. Referential Integrity prevents this from happening. The Edit Relationships dialog box can also be displayed by clicking the Edit Relationships button in the Tools group on the Design tab. Creating Queries You ll be in the Query Design View when creating a Query. The Query Design View has two major sections. In the top section, the Table(s) and/or Queries used for this Query are displayed along with the available fields. In the bottom section, those Fields that have been selected for use in the Query are displayed. Each Field has several options associated with it: Field - The name of the Field from the Table Table - The Table the Field comes from Sort - The order in which to sort on this Field (Ascending, Descending or Not Sorted) Show - Whether or not to display this Field in the Query output Criteria - Indicates how to filter the Records in the Query output. Setting Conditions in a Query Sometimes you ll want to run a Query which will return specific values or a range of values in one or more Fields. You can use operators such as <, >, =, etc. to do this. These are known as comparison operators and conditional operators. Setting conditions in a Query means that you can retrieve or manipulate data selectively. This can be done in the Criteria line of the Query in the Design View. Below we are looking for Orders with a Shipped Date after 04/01/2006 (i.e.: >4/1/2006). Also, we are looking to Query only the Orders which have a quantity that is greater than 100 (i.e.: >100). Access Handout Page 6 Spring 2011

7 In the above image you can also see that the Order Date Field from the Orders Table will be sorted in Ascending order. A drop-down menu will appear when you click on the Sort area beneath any of the Fields. From this drop-down menu you can select Ascending, Descending or (Not Sorted). Other examples of Criteria Statements might look something like this: = NH as a value in a State Field. This would restrict the output to only states with a NH code. >1000 And <2000 as a restriction to a Purchase Price field. This would restrict the output to only items greater than $ , but less than $ B* in a Customer Name field. The * acts as a wild card and would restrict the output to only Customers whose names begin with B (e.g. Bachmann, Bismark Inc., etc.). To run the Query when you are in Design View, either switch to Datasheet View or select the Exclamation Point (!). Forms A Form is nothing more than an organized and formatted view of some or all of the Fields from one or more Tables. You can add, update, or delete Records in your Table by using a Form. Note that although a Form can be named different from a Table, they both still manipulate the same information and the same exact data. Hence, if you change a record in a Form, it will be changed in the Table also. A Form is very good to use when you have numerous Fields in a Table. This way you can see all the Fields in one screen, whereas if you were in the Table view (datasheet) you would have to keep scrolling to get the Field you desire. Below is an example of a Form as seen in the Design View: Access Handout Page 7 Spring 2011

8 Label controls Text box controls The controls you will use most frequently in an Access Form are: Text box controls: You can view or enter information in these controls. Think of a text box control as a little window through which you can insert data into the corresponding field of the related Table or view information that is already in that field. Label controls: These tell you the type of information you are looking at in the corresponding text box control, or what you are expected to enter in the text box control. Creating a Form Using the Form Creation Tools There are a few different ways to create a Form: By clicking the table you want in the Navigation Pane, and then clicking the Form button in the Forms group on the Create tab. This method creates a simple Form that uses all the Fields in the Table. By using a Wizard. This method enables you to choose which of the Table s fields you want to use in the Form. Manually in Layout View where you can see the underlying data or Design View where you have more control over Form elements. For example, to generate a simple Form from a Table: 1. Select the Table by clicking once on it in the Navigation Pane. 2. On the Create tab, in the Forms group, click on Form. Access Handout Page 8 Spring 2011

9 3. Once the Form is generated, on the Quick Access toolbar, click Save. 4. In the Save As dialog box, in the Form name text box, specify a name and click OK. This option will take one Table with all of its Fields and present it in an aesthetically pleasing manner. To enter data using the Form, use the arrows at the bottom of the page to proceed to the entry you wish to change or to add another entry. If, however, you need multiple Tables, and want to pick and choose which Fields to include in your Report, you should choose the Form Wizard, also on the Create tab in the Forms group. This will walk you through a step-by-step process in which you choose which Tables to include and which Fields. Reports A Report provides an object used to print a database's records. Although you can print Tables or Forms, Reports are customized to be printer friendly. Whether your Report is a simple listing of records or a grouped summary of, e.g. sales by region, the first step is to determine which Fields contain the data you wish to see in your Report, and in which Tables or Queries they reside. After you choose your record source, you will usually find it is easiest to create your report by using the Report Wizard. The Report Wizard is a feature in Access that guides you through a series of questions and then generates a Report based on your answers. It provides options for grouping and sorting data, as well as tools for customizing the Report s layout. 1. On the Create tab, select Reports, then Report Wizard. 2. Select the Tables and/or Queries on which to base your Report, and then click Next. Access Handout Page 9 Spring 2011

10 3. Continue selecting your Grouping Levels, Sort Sequence, Layout and Title. 4. Select Preview the Report and then Finish to view the report (Print Preview). 5. Close Print Preview to return to Report view, or Layout or Design view to modify your report. Note another method to create a Report is to select your data source (Table or Query) and then select Create, Reports, then Report. This will create a simple Report based on the data source that you can modify in Layout or Design view. Sources: Element K. Microsoft Office Access 2010 Level 1. New York: Element K., Cox, Joyce. Microsoft Access 2010 Step by Step. Redmond, Wash.: Microsoft, Access Handout Page 10 Spring 2011