Microsoft Access 2007 Lesson 1: Creating and Editing a Database

Transcription

1 Microsoft Access 2007 Lesson 1: Creating and Editing a Database Databases are collections of information that are organized so that you can easily find the information that you need. It is fairly easy to retrieve information from small databases, such as a phone book, which is organized alphabetically by last name. On the other hand, large databases, such the itunes catalog of over 5 million songs (July 31, 2007), are too massive to be navigated by hand. Large databases require a separate computer program, called a database management system (DBMS), to help manage and retrieve information. You are using a DBMS whenever you use itunes searching tracks according to artist, album or genre and creating playlists, for example. These lessons will introduce you to a DBMS that is accessible and fairly easy to use, Microsoft Access. Downloading Files for Lessons The files you need for this lesson are located at the URL below: You will see a list of files. Right-click on the first link and choose Save Target As... in the menu. Save the file to your H: drive. Repeat for the other files on the list. Database Concepts Access is structured in terms of tables that have rows and columns and look a lot like an Excel worksheet. Columns in the table, which are called fields, identify the types of data that are stored in the table Last Name, First Name, Middle Initial, Street, City, and State in the example shown below. Each row in the table, which is called a record, is a set of information about a particular item in the database a particular person in the example shown below. 10/29/2009 1

2 The data elements of a database at the intersection of a row (record) and a column (field) are called values. For example, the value of the First Name field for the second record in the table shown above is Alfred. One of the fields, called the primary key, in a table uniquely identifies each of the records. In the example shown above, the primary key is the ID. No two rows in a table can have the same value in a primary key field. Access is a relational database management system (RDBMS) that generally uses more than one table to store information. Each table holds data that are logically inter-related. For example, a college student database might have one table of personal information about students and another showing the classes they are taking. These two tables have a relationship created by the matching StudentID numbers. For example, by matching the two StudentID numbers we can see that Bat Masterson took Psychology 104, Humanities 100, Math 200, and Religion 202 in the term. If a database contains a large number of fields, a one-table database will be very large and unwieldy. Grouping data in multiple tables usually allows it to be maintained and manipulated more efficiently. NOTE: You will find these lessons interspersed with Questions and Practice Problems. These are integral parts of the lessons and should be done at the time you read them rather than later. 10/29/2009 2

3 In Class Question: Suppose you were storing the data on page 2 in one table, like the one below, rather than two. Would this lead to more work entering data and an increased chance of making errors? (Hint: Think about Alfred E. Neumann, for whom class data is shown in both the and terms.) What kind of duplication will be required when you enter a record for one term and then for another? How would you store data for a student taking five classes in a semester? Searching in several smaller tables also is more efficient because it is easy to create queries that can pull information from multiple tables. A Database Example Let s assume that your hobby is collecting old 45 rpm records from the classic rock era of the 50s and 60s. You decide to create a database to help you manage your collection. We will create an Access database to store the following information about your collection: Label No. Artist A-side B-side Condition Price Swan 4152 Beatles She Loves You I ll Get You Excellent $ Swan 4152 Beatles She Loves You I ll Get You Fair $ Swan 4152 Beatles She Loves You I ll Get You Poor $ Capitol 5555 Beatles We Can Work It Day Tripper Good $ Out Soma 1137 Fendermen Muleskinner Torture Good $8.50 Blues Soma 1137 Fendermen Muleskinner Torture Fair $5.00 Blues Decca Haley, Bill and See You Later The Paper Excellent $12.00 the Comets Alligator Boy Mercury Platters I m Sorry He s Mine Fair $15.00 Volt 157 Redding, Otis (Sittin On) The Dock of the Bay Sweet Lorene Good $6.50 Notice the duplication in several fields in this table (for example, in the first three Beatles records). To remove the duplications, we will construct the database with more than one table. In this case we will use two tables, one to store information about each 45 record and one to store information about the copies of that record that you have... Recall that each table must have a primary key field. We will add unique IDs as primary keys in the two tables. ID45 will identify a 45 rpm record that was issued. IDSpecific will identify a specific copy you own. Instead of storing a word for the condition, we will use one letter (e.g., E for Excellent ) to specify the condition, which will make data entry easier. 10/29/2009 3

4 tblissue ID45 Label No. Artist A-side B-side 1 Swan 4152 Beatles She Loves You I ll Get You 2 Capitol 5555 Beatles We Can Work It Out Day Tripper 3 Soma 1137 Fendermen Muleskinner Blues Torture 4 Decca Haley, Bill and the Comets See You Later Alligator The Paper Boy 5 Mercury Platters I m Sorry He s Mine 6 Volt 157 Redding, Otis (Sittin On) The Dock of the Bay Sweet Lorene tblvalue IDSpecific ID45 Condition Price 1 1 E $ F $ P $ G $ G $ F $ E $ F $ G $6.50 In Class Question: Each row in the tblvalue table is associated with a row in the tblissue table. What field in each table establishes the relationship between the two tables? Opening Access Having figured out the tables we need, we are ready to create our database. Open Microsoft Office Access. When Access starts you will see a screen that looks something like this one. 10/29/2009 4

5 Creating a New Database Choose Blank database from the New File menu at the right. In the Blank Database section that appears on the right side of the screen, click on the Folder icon to choose where you want to save the database. Navigate to your H: drive and choose the name Records for your database. Click on OK. You should see the File Name Records.accdb, with H:\ below it. Click on Create. 10/29/2009 5

6 Creating Tables in Design View First we will create a table with the field names shown below. ID45 Label No. Artist A-side B-side Click on the Design View button. Name the table tblissue. You now should see the Design View of the table the view we use when we want to work on the structure of the database, as opposed to the data stored in the database. The Design View allows you to enter names of the fields in the table and to specify their data types. A data type indicates the kind of data to be stored for example, numbers, text, or dates. It is best to select the type that most closely matches the kinds of values you are storing in a field. 10/29/2009 6

7 When you design a table, the first thing you do is to specify the Field Names and the Data Types the type of data that is allowable for each field. A few common data types are listed below: Data Type Allowable Field Values Number of Characters Text (the default data type) Letters and numbers Up to 255 Number Numbers Up to 64,000 AutoNumber Numbers in sequence that are automatically created by Access Currency Numbers Date and time Numbers The first Field Name we will enter is ID45, the field we will use as the primary key to uniquely identify each record. Enter ID45 as the first field name. Its Data Type should be AutoNumber. The new field probably will be designated as the primary key for the table see if there is a small key icon to the left of the field name. If the ID45 field has not been designated as the primary key, rightclick on the Field Name. In the menu that pops up, select Primary Key. Enter Label as the second field name. The default Data Type is Text, which is appropriate for this field. You will see a list of Field Properties at the bottom of the Design View window. The default Field Size for a Text field is 255, which is much bigger than a record label name is ever going to be. Change the Field Size to /29/2009 7

8 Enter the other Field Names as shown at the right. Use 100 as the lengths for Artist, A_Side and B_Side. When you have entered them, click on the Save icon to save the table. In Class Practice: Creating as Second Table Select the Create tab and click on Table. Name the table tblvalue Add the four fields shown on page 4 for the table labeled tblvalue o Choose the appropriate one of these fields to be the primary key Assign a Data Type appropriate for each field. The Data Type for the Price field should be Currency. Adding Data to a Table Now that the tables have been created we need to populate them with data. We will start with tblissue. Select the tblissue tab and choose Datasheet View from the View menu. 10/29/2009 8

9 This will display the Datasheet View of the table the view in which you add data to the table. This view is reminiscent of a spreadsheet. Each column is labeled by a field name. The Home tab should be selected. If it is not, click on the Home tab to select it. Enter the data in the table below into the database. Don t type anything in the ID45 field, which is autonumbered. Every time you make an entry of a new Label, the next number will automatically be added to the corresponding ID45 cell. When you have entered the data for one cell, pressing the Tab key will move to the next cell on the right. ID45 Label No. Artist A-side B-side 1 Swan 4152 Beatles She Loves You I ll Get You 2 Capitol 5555 Beatles We Can Work It Out Day Tripper 3 Soma 1137 Fendermen Muleskinner Blues Torture 4 Decca Haley, Bill and the Comets See You Later Alligator The Paper Boy 5 Mercury Platters I m Sorry He s Mine 6 Volt 157 Redding, Otis (Sittin On) The Dock of the Bay Sweet Lorene When you have entered the data, you may find that the column widths do not match the data in the fields. For example, the Label column is consistently wider than the Label names that have been entered. On the other hand the columns for the Artists names and song titles are too narrow. 10/29/2009 9

10 Using the same methods as for spreadsheet columns, either drag the column borders or doubleclick on them to change the column widths to match the data. Click on the Office Button and Save the file. Select the tblvalue tab and move to Datasheet View. If you are asked whether you want to save the table, choose Yes. Add the data shown at the right to the table. The contents of the IDSpecific field should be autonumbered and cannot be entered. Enter E for Excellent, G for Good, and so forth. Do not type the dollar sign for the monetary values because the Data Type for this field is Currency, the dollar sign should be displayed automatically, Save the file. Right-click on the tblvalue tab and close the table. Editing Data You can change the values stored in the database at any time. Suppose you decide you want the name of the Otis Redding A-side to be simply The Dock of the Bay, rather than (Sittin On) The Dock of the Bay. In the tblissue table, click on the cell containing (Sittin On) The Dock of the Bay. Delete the characters you do not want. Save the table when you are finished. 10/29/

11 Adding a Field Even if you have planned carefully in advance, it is not unusual to find you need to add a field once you actually start using the database. In our example, after using the Records database for a while, you find that you need a field to show that date on which you purchased each specific recording. We will add this field to the tblvalue table. Open tblvalue by double-clicking on the table name in the list of tables. In the Design View, enter a field with name DatePurchased and Date/Time type. Note that there is no space between the two words in DatePurchased. Save the table. Move to the Datasheet View. This view will display the contents of the table, including the new DatePurchased field, which currently contains no data. 10/29/

12 Setting Field Properties Before entering data in the new field, we will set a few Field Properties. Return to the Design View and select the Condition field name. Enter the Description and Field Properties shown here. We will describe the function of these entries below. Save the table. When you do, you will be notified that a field size has changed and some data will be lost. This is because we reduced the field size of the Condition field. Don t worry about it because the change will have no effect on the data in the field. Field Description The Field Description gives the user information about what kind of data may be entered in that field. In the Datasheet view, when you are entering data, the Field Description is displayed at the bottom of the Access window, as shown in the illustration at the right. 10/29/

13 Field Properties: Format Property The Format property specifies the way that data is displayed. It does not change the way that the data actually is stored in the database just how it is displayed. A few format examples are given in the table below: Format Symbol Data Display Example > All characters displayed as uppercase If a field is formatted with >, data entered as e would be displayed as E < All characters displayed as lowercase If a field is formatted with <, data requires a text character or space to be entered. as G would be displayed as g If a field is formatted data entered as would be displayed as (864) This is useful for phone numbers, for instance. Choosing the Format = > for the Condition field means that all entries in that field will be displayed as uppercase. Then you don t have to worry so much about whether you enter E or e as the condition. For some data types, you can choose a format property from a list. For example, move to the DatePurchased field, which has a Date/Time Data Type. If you click on the white rectangle next to Format, you will see an icon appear. Clicking on this icon will display a list of date formats from which to choose. For our example, choose Medium Date, which will display the dates like 19-Jun-07. Go into Datasheet View and enter dates in the empty fields. Notice that dates always are displayed in Medium Date format (e.g., 19-Jun-07) even if you enter the date in another format (e.g., 6/19/07). Save the file and return to the Design View. 10/29/

14 Field Properties: Validation Rule and Text Databases often include Validation Rules that limit the input that is possible in a field. When you make an entry in a field, Access checks your entry against the validation rule (if any) that has been set up for that field. If the entry agrees with the rule, then everything is OK. If the entry violates the validation rule, an error message will be displayed showing the validation text. For example, the only entries possible in the Conditions field are E, G, F, or P. The validation rule shown at the right limits entries to these four letters. In Class Practice: In Design View, enter the validation rule shown above Go to the Datasheet View of the table and try to enter B for Bad as a Condition. Does B satisfy the Validation Rule set up for this field? What role does the validation text play when you enter B? Moving a Field After using the database for a while, you may decide to change the position of one of the columns or to remove it entirely from the table. Suppose, for example, that you want to move the DatePurchased column of tblvalue two columns to the left so that it is between the ID45 and Condition columns. Move to the Datasheet View and select the Home tab. Then click on the Field Label (DatePurchased) so that the entire column is selected. Grab the column by clicking on the Field Label and holding the left mouse key down. Drag the column to the left until a solid line is displayed where you want to drop the column. 10/29/

15 Drop the column in the new position by releasing the mouse button. Deleting a Field If you find that you never use a field in the database, you may decide to delete it. This only should be done after giving the deletion careful thought, because deleting a field deletes this information from every record in the database. Always back up your database before deleting a field in case you want to restore it later. You cannot use Edit, Undo to undo the deletion of a field. Let s delete the DatePurchased field from tblvalue. Move to the Datasheet View and select the Home tab. Select the entire column by clicking on the Field Label. Click on Delete icon. Access will ask you if you really want to do something this drastic. Click on Yes to delete the field. Save the database. 10/29/

16 Deleting a Record At some point, you probably will want to remove one or more records from the database if, for example, you sell one of the 45s in your collection. Once a record has been deleted it cannot be restored without re-entering the data. Always back up your database before deleting a record in case you want to restore it later. Open tblissue in the Datasheet view. Select the Home tab. Suppose that you have sold the Platters record and want to remove it from the database. Click on the far left of this record to select the entire record. Then click on the Delete icon. You will be asked to confirm that you really want to do this. Click on Yes. Note: as an alternative to deleting a record for a 45 you no longer have, you could add a field that designates the date a record is sold. If a sold-date value is present in a row, then that record has been sold. If a sold-date value is null (not present), then the 45 has not been sold yet. This design lets you keep a history of your collection. Consider such alternatives when you design a database. 10/29/

17 Print Preview and Printing a Page Open tblissue in Datasheet View. To preview what the printed version of the table will look like, click on the Office Button and then hold the cursor over Print for a second or two. When a Print menu appears, click on Print Preview. You probably will see something like the picture at the right. Note that the entire table does not fit on the page because the orientation of the page is set to Portrait. We need to change the page layout to Landscape. In the Page Layout section, select Landscape orientation. This will orient the page so that the entire table will be displayed on one page. Although we will not do it in this lesson, you could now choose Print on the Office Button to print out a hardcopy of the table. Save and Close the Records database. 10/29/

18 More About Field Properties Click on the Office Button and 0pen the database named ExampleDB that you downloaded into your H: drive. You will see that this database has only one table, tblemployees. Open this table. Change to Design View and set the text Field Sizes to those shown below: LastName 25 FirstName 25 MI 1 Street 25 City 25 State 2 Save the database. Because you have decreased some of the field sizes, you will be warned that data might be lost. The field sizes above are more than sufficient to hold the data, so do not be concerned about this warning. 10/29/

19 Field Properties: Default Value In this table, we see that most of the states are SC. Choose the Default Value field property for State and enter SC. When a default value, such as SC, is set this value will automatically be entered when a new record is created. It can be changed if need be. Also set State s Format property to >. Finally enter the Description Enter the two-letter abbreviation for the State field. In Class Question: What does setting the format property to > do? Field Properties: Input Mask An Input Mask lets you designate the way data may be entered for a particular field, thereby reducing the probability of data input errors. The Input Mask property is different from the Format property. The Input Mask property limits the way that data can be entered and hence defines the way that data actually exists in a table. The Format property limits the way that data is displayed not how it is stored. Let s use an input mask to designate how phone numbers may exist in the table. In Design View, select the Home Phone field and click on the Input Mask property. You will see a small button with three dots displayed at the right of the Input Mask row. Click on this button. You will be asked if you want to save the table first. Click on Yes. 10/29/

20 In the Input Mask Wizard window, select the Phone Number input mask. The appearance that this mask will give to the data is shown in the Data Look column. Using this input mask, phone numbers will look like (206) Click on Next. In the following window, you will be asked if you want to change anything. Let s not change anything. Click on Next again. You next will be asked if you want the stored data to include the symbols in the mask. This is useful in the case of phone numbers, so let s do it. Select the top option. Click on Next and then Finish. The expression for this Input Mask now is displayed. If you Save the database and look back at the Datasheet View, you will see that the phone numbers now are stored in the format specified by the Input Mask. Enter a new record or two in the table to see how the Input Mask works. 10/29/

21 Field Properties: Captions It is useful to give fields names that do not include spaces. Although Access allows field names with spaces, not all DBMS do. It also is easier to write SQL statements if you don t include spaces. On the other hand, people are accustomed to seeing spaces between words, so we would like to label columns in tables with spaces included. We can do this by defining captions for fields. Define a caption for fields that need spaces between words. For example the field LastName has no spaces between the two words. We can choose its caption to be two words: Last Name. If you look at the Datasheet View, you will see the captions displayed at the top of the columns rather than the actual field names. In Class Review: Creating a Table Create a new table in the example database named tbldepartments, which contains two fields. The first field, the primary key, will contain numbers. Name this field DeptID. Note that the Dept ID field is a Number field and is not autonumbered. The second field, named DeptName, will contain text. Make the entries shown below in the table. Save the table. DeptID DeptName 100 Purchasing 101 Finance 102 Shipping 103 Sales 104 Personnel 105 Marketing 106 Security 107 Engineering 108 Communications 109 Information Technology 10/29/

22 Importing Records into a Database When creating a database, it may be that some of the data you need already exists in an Excel spreadsheet, for example. If this is the case, you probably will want to import the existing data into your database to avoid entering it again by hand. In our example, information about salaries and whether employees are exempt from receiving overtime pay is stored in an Excel spreadsheet named Salaries, which you downloaded into your H: drive. We want to create a new table in the ExampleDB database from the Excel spreadsheet. Close all tables in ExampleDB. Select the External Data tab and click on the Excel button. Select Import the source data into a new table in the current database. Click on Browse. Find the spreadsheet file named Salaries located on your H: drive. 10/29/

23 The spreadsheet has three worksheet tabs, so Access will ask you which one you want to use. We will use the first sheet, which is the only one that contains data. Click on Next. You will be asked if you want to use the Excel column headings as Field Names in the table you create. In this example, we do. Click on Next. We will use the Employee ID field as a Primary Key, so we do not want it to have any duplicates. Choose Yes (No Duplicates) in the Indexed drop-down box. Click on Next. 10/29/

24 Choose Employee ID as the Primary Key for the table. Click on Next. Finally, enter the name of the table let s call it tblsalaries. Click on Finish. You will be asked if you want to save the import steps. Generally you will not. Do NOT check the Save import steps box and click on Close. 10/29/

25 You now will see tblsalaries included in the list of tables in the database. Finally, add captions to the Field Properties of tbldepartments and tblsalaries as needed. Save the database. Exercises (To be done outside of class.) 1. What is the difference between the Datasheet and Design Views in Access? What do you use the Design View for? What about the Datasheet View? Where is the icon on the Access toolbar that toggles you back and forth between these two views? 2. What is a primary key in a table? Why is it necessary? 3. How is a RDBMS different from a DBMS? 4. What is the purpose of the Autonumber format? 5. What is the difference between a field description and a validation rule? How is each used in Access? 10/29/

26 6. Look at the table of data below: City State Office Phone Staff Chicago IL Cicero (773) Bill Jones Chicago IL Cicero (773) Jill Kirby Chicago IL Cicero (773) Jon Gaff Chicago IL Oak Park (773) Mary Arthur Chicago IL Oak Park (773) Virginia Dawes Chicago IL Oak Park (773) Alfred Prufrock Chicago IL Berwyn (773) Tillie Mays Chicago IL Berwyn (773) John Illkie Chicago IL Berwyn (773) Kirby Puck Chicago IL Addison (773) Jonica Kinsey Chicago IL Addison (773) Bubba Ames Chicago IL Addison (773) Chris Armstrong Atlanta GA Doraville (404) Otto Engine Atlanta GA Doraville (404) Frank Hucks Atlanta GA Doraville (404) Linda Dyson Atlanta GA Roswell (404) Juanita Masters Atlanta GA Roswell (404) Aaron James Atlanta GA Roswell (404) David Demster Atlanta GA Downtown (404) R. K. Lings Atlanta GA Downtown (404) Reba Newling Atlanta GA Downtown (404) Watts Yterby How many Access tables would you set up to store this data efficiently? Decide on the fields you would use in each table. What would be the primary key in each table? What would be the relationships that link the tables? 7. You enter Elmer Fudd in a field that has the < Format. In what form will this name be displayed on the screen? In what form will it actually exist in the database? 8. You enter Elmer Fudd in a field that has the < Input Mask. In what form will this name be displayed on the screen? In what form will it actually exist in the database? 9. Define a format mask for a field that contains a nine-digit phone number so that the value displays as /29/