Access1

Introduction to Microsoft Access

Part 1 - Tables

Tables are a fundamental requirement of any database. To get valuable information from a database, you first have to have data. All your data will be stored in tables.

1. Creating a Relational Database in 30 Seconds!

1. Start up Access

2. Use the Database Wizard

3. Select the Music Collection wizard

4. Save the database file in your My Work folder

5. The Wizard starts. Click Next.

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6. The Wizard then tells you what tables there will be in your database and what Fields each table will contain. You can tick or un-tick any field to customise your database. Click Next when done.

7. You then get to select a colour scheme. Click Next when you’re happy.

8. You will then be asked to choose a report style and finally you will be invited to name the database. Click Finish when you have answered all the questions in the Wizard. The database will then be created.

Your database is now created and, as promised, the whole process should have taken no more than 30 seconds. We will now take a tour of the database window.

9. You are presented with a Switchboard window. This is an interface, which can be created to make the database user-friendly.

10. Click the Enter/View Recordings button. The Recordings Form is opened. Try entering details of some of your favourite albums.

11. Close the Recordings Form and close down the Switchboard (click the cross in the top-right corner of a window to close it down).

12. Although you have closed the Switchboard, the database is still open. Double-click the Music Collection Database window, which is currently minimised in the bottom-left of the Access window.

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13. You will see that an Access Database consists of Tables, Queries, Forms, Reports, Macros and Modules, all of which are stored in the Database Window as separate objects. If you take a tour of this window, you should see that the wizard has created tables, forms and reports in the music collection database. You can double-click each object to open it. Some of the forms should be familiar to you because you have previously opened them via the Switchboard.

14. If you open the Tables, you should see that the only data in the database, is the sample data you entered into the Recordings Form. Although you entered this data in the Recordings Form, you should see that this data is being stored in several tables. The form was created to provide an easy interface for the user to enter the data.

You should, by now, realise that data entry forms and switchboard forms are provided for the convenience of the user. As a database designer, you will want to make your database very easy to use. You will also see that good database design can ensure that the data entered is accurate.

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2. Start with a Blank Database

Unfortunately, you won’t learn how to be a database designer by using the Database Wizard! Now is the time to create a database from scratch.

1. Click on File and New Database.

2. Create a New Database using the Blank Database.

3. Give your database a Filename.

4. You should now have a blank database Window open at the Tables tab. Click New to create a new table and select Table Wizard.

5. Click OK and you should see a screen, which gives you a wide choice of sample tables and fields for business and personal use.

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6. Choose a personal table and select all the fields from the Recording Artists sample table. Your screen should look like this:

7. Allow the Wizard to set a Primary Key and change the selection on the last screen, so that you are going to modify the table’s design after the wizard is finished. You should finish with a screen that looks something like this:

It is worth studying this screen for a while. You should see that the Wizard has set the Fields, including RecordingArtistID, which is a Primary Key. You should see that each field has a Data Type (e.g. Text, Number, Date/Time) and they also have Field Properties, which includes a Field Size setting.

8. Close the Table’s Design View and you will see that the Recording Artists table is now shown in the database window. Click the Right Mouse Button on the table and select Rename. Change the name to Artists.

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3. Understanding Your New Table

1. First, let us try to understand what the Wizard did. You now have one table in your database (called Artists). If you open this table in Datasheet View you can start entering data into it.

You might notice several things: The RecordingArtistID field assigns a unique number to each record that you

enter. The Birth Date field only allows you to enter valid dates. Try entering an

invalid date (e.g. 45/13/02). The birth dates entered above are made up. Try using the Internet to research the real D.O.B.s for your favourite artists.

You can write as much as you want in the Notes field. It would be a good idea to adjust the width and height of the columns (as above).

2. Once you have entered several records, you can try to search your table. To do this, click in the column in which you wish to search and press CTRL+F (or select Find from the Edit menu). Perform a few simple searches using this method.

3. If you don’t understand these terms already, it is high time that you learnt the jargon:

Data Stuff you put into your databaseFields A place for your data to live

e.g. a database of footballers would have fields such as FirstName, LastName, Position, Team etc.

Records A record groups data together in an orderIf it wasn’t for records, your database wouldn’t know which last name went with which first name.

Table A collection of records that describe similar dataIn a flat-file database, all the data goes into a single table. However, Access is a “relational” database, meaning that you can create many tables and link them together.

Database File A collection of tables and also various other tools to assist in the use of the data e.g. queries, forms, reportsEverything is compressed together in a single file with an MDB extension

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4. Creating a Table Without the Wizard

1. Now you should try to create a table without any wizard help at all. To do this, you create a new table in Design View.

You are presented again with the Table Design View screen but, this time, no fields have been created for you.

2. Enter the fields as follows:

N.B. Make sure you do the following: Make RecordingID a Primary Key (click the Right Mouse Button in the

grey area next to the field name) Make sure the correct Data Type is set for each field (these will be explained

later) The only field size you have to set is for the Title and Label fields. Select a

suitable size (a little larger than you think you will need). Leave no spaces between field names Enter a description for each field

For Discussion

Why should field sizes not be too big? Why should field sizes not be too small? How can you enter a Default Value for a field and what is the purpose of

doing this? Why shouldn’t you put spaces in field names? Why bother entering a description? What is the purpose of a Primary Key? Can a table have more than one Primary Key?

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4. Close the table design view and name the table Albums.

5. Re-open the Artists table in Datasheet View. Try adding a record. Then try deleting an existing record.

6. Create a new table called Tracks with the following fields:TrackID (Primary Key, AutoNumber)RecordingID (Number)TrackNumber (Number)

7. Create a fourth table called Categories, as follows:CategoryID (Primary Key, AutoNumber)Category (Text)

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5. Help and Helplessness

1. You can press F1 for Help, at any time (try it)

2. The Office Assistant is now always as helpful as he could be. To get real help, look in the Help Menu:

3. Select Contents and Index to see the full Help system. The Index tab gives you a full alphabetical index of help topics. The Find tab, allows you to search for a topic to get help on.

4. The What’s This? Feature is particularly useful. Select this item from the Help menu and your cursor will change to an arrow with a question mark beside it. You will get help on the first thing you click on. You can ask Access “What’s This?” at any time. Try selecting What’s This and clicking on the Design button of the Table Window:

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5. Access has 22 button bars, which change depending on what you’re doing. There are so many buttons that nobody could ever hope to remember what they all do. To make life easier for you, there are Screen Tips, which pop up when you hold the mouse button over a button (try it).

6. Get into the habit of using the Right Mouse Button. In Access, when you click on something, it invariably brings up a menu. For example, try clicking the Right Mouse Button on one of your tables. You can see that you now have options such as renaming, printing or deleting the table. You can also open the table in Design or Datasheet view from this menu.

7. Saving your work in Access is very easy. Access Autosaves most things (for example, each record is saved as soon as it is created). This is a benefit but also a danger because, for example, if you delete something by accident, Access will not question your decision! Pressing Ctrl+Z or select Undo from the Edit menu will usually undo the very last thing you did but don’t rely on this to get you out of trouble.

8. Backup is essential and also very easy. Access saves all your tables, queries, reports etc. in one handy file with an MDB extension. Your early databases will easily fit on a floppy disk:

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6. Data Types

You have now created four tables and you have set a data type for each field that you have created. You have also tried entering data into the tables and you have noticed that certain fields will not allow certain types of data. For example, you can’t enter an invalid date into a date field. You can’t enter text into a number field.

In your tables, try to find examples of each of these data types (you will find most but not all). Why have the data types been set in this way?

AutoNumber Automatically generates a number each time you add a record. This number is used as a unique identifier for each record.

Text Stores letters, numbers and any combination thereof. Can be up to 255 characters in length

Memo This is a really big text field. Holds up to 64,000 characters (about 18 pages of text).

Number Holds numbers and decimal points but nothing else. Set a field to Number if you want to do calculations.

Currency Formats money fields. Date/Time Either the date or the time or both, in a variety of formatsYes/No For fields where one of two answers is required. You can have

Yes/No, True/False or On/Off. It is possible to add your own variants.

OLE Object You can add photographs, sounds etc. in a field of this data typeHyperlink For webpage addressesLookup Wizard Prevent errors by presenting the user with a list of acceptable

answers to choose from.

For Discussion

Why are telephone number fields usually set to text? How does setting the right data type help prevent bad data being

entered? You can enter numbers into a text field. Apart from the fact that it

guards against bad data, why should anyone want to bother creating a number field?

Why not set all text fields to Memo?

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7. Flat File or Relational?

A Flat File database contains a single table. Flat File Databases are very easy to create and use. They are ideal for simple things like databases of address books, video collections, and so on. They are similar to the traditional desktop “card-file”.

Relational databases have multiple tables that are linked together with “key fields”. Relational databases really shine when they are used to solve big business problems. A whole business can use one database that integrates the whole organisation.

You need to understand why flat file databases are inadequate for big tasks.

This is a simple database for a library:

There are three tables – Books, Borrowers and Loans. When the library gets a new book, it enters its details into the Books table. All the members of the library have their details entered into the Borrowers table. When someone borrows a book, the Loan table is used. The information about the book and the borrower does not have to be entered each time a loan is made because this information is taken from the Book and Borrower tables. This is indicated by the lines that link the tables together. These links are known as relationships.

The symbols at each end of the line indicate what type of relationship exists:One to One: Each book can only be borrowed onceOne to Many: One borrower may borrow many books

Your Task

Imagine that you have to set up a database for a library but you only have a flat file database application.

Design the table that you will use and describe how the system will work. List all the problems you encounter Write a report to the library committee telling them why they ought to invest

in a relational database system, such as Access.

8. Build Relationships for the Music Database

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1. Click the Relationships button on the toolbar or select Relationships from the Tools menu.

2. The Show Table window will ask you which tables you want to display in the Relationships Window. Select all four of your tables and then close the Show Table window.

3. You can adjust the size and the position of the four tables in the Relationships Window.

4. To build a relationship between fields, click on a field with the Left Mouse Button and drag it onto the field you want to link to. A window appears asking you to confirm the relationship. Here, you also have the chance to change the type of relationship.

Things to watch out for: Linked fields must be identical (same data type, same size, same name) Select Enforce Referential Integrity and Cascade Update Related Fields if

you want to update corresponding values in a related table when the primary key value is changed.

Your Task

You have to create relationships for your tables to reflect the following facts: One album has many tracks One artist may have recorded several albums There may be several albums in the same musical category

When you have finished, you should have something like this:

If the symbols at the ends of the relationship lines don’t match, try changing your join settings. To edit a relationship, double-click on a join line. To delete a relationship, click the line once and press the Delete key. Close the Relationships Window when you’re finished.

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9. Index Your Fields

You will now return to the Table Design view to “tweak” your tables for greater efficiency. The first thing to do is to index some of your fields.

The purpose of indexing your fields is to speed up sorts and queries. You should not index every field because too many indexed fields slows down data entry.

You have to index each of your fields in turn. To do so, select a field and click the Index section of the Field Properties.

Your three options are:

No Don’t index the fieldYes (DuplicatesOK) Most of the time you want to allow duplicate records. Yes (No Duplicates) Key fields should be set to No Duplicates because a key

field must be unique. You don’t want two customers with the same customer number.

You can see a list of indexed fields by clicking the Indexes button on the toolbar.

For Discussion

You should set the Index to No Duplicates when the records have to be unique (for example, a key field must be unique.

What other fields could be set to No Duplicates?

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10. Formats

Staying in the Field Properties, we will now check to see if a Data Format is appropriate.

You use a format if you want to change the way your data appears on screen.

Each field type has its own set of formats. Some of the most commonly used are as follows:

Text and Memo Formats

Symbol Meaning What it Does> Greater than Makes all text appear in

upper case< Less than Makes all text appear in

lower case

Number and Currency Formats

General Number Default optionCurrency Displays numbers as currencyFixed Locks the field to display a specified number of decimal

placesStandard Adds a thousands separatorPercent Displays decimal places as a percentage

In a number field, you can change the Field Size setting from Long Integer to Single if you want to dispense with decimal places. However, if the field is part of a relationship, you should be aware that an AutoNumber field must be set to Long Integer.

Date/Time Formats

You have a choice of how the date/time is displayed

Yes/No Formats

You have three initial choices, which are Yes/No, True/False and On/Off. You can add your own selections to this list.

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11. Input Masks

The aim of an Input Mask is to prevent the user entering bad data. The great danger in using them is that you might end up preventing the user from entering correct data. For this reason, you must think carefully before deciding to set an input mask for a field.

An input mask is a series of characters, which tells Access what kind of data to expect. Each field can have an input mask, with the exception of a memo field.

Input Masks work best with highly consistent data, such as phone numbers, national insurance numbers and postal codes.

You can either write your own input mask or you can use the Wizard. To use the Wizard, click the Build button, which appears when you click the Input Mask Property.

Your Task

Create an Input Mask for a telephone number and then test it. Try entering a variety of valid postal codes and make sure they are accepted. Try international and mobile telephone numbers.

For Discussion

Would the telephone number field be better off not having an input mask?

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12. Validation and Required Fields

Together with Input Masks, validation tests and required fields are your weapons in the war against bad data.

Using the Required property is easy because there are only two choices – yes and no. Set the Required property to Yes if you want to force the user to enter something in this field.

For Discussion

When would you want to set a Required property to Yes?

What would happen if you set all fields to Required?

The Validation property is more sophisticated because it performs a test on incoming data to make sure it’s what you want.

Two properties require your attention:

Validation Rule The test that will be applied to the dataValidation Text This is a message, which Access will

display if the data is unacceptable (i.e. if it fails the validation test).

Validations work best with number, currency and date fields because the incoming data is more predictable. The Validation Rule is written as an Expression.

An Expression is an instruction that you give to Access in a language that Access can understand. For example, if you want to force users to enter only positive numbers in a number field, the expression is “> 0” i.e. the number must be greater than zero.

Try some of these expressions on some of your fields and see what happens. Mix and match the operators and see what you can come up with:

> 0 Must be greater than zero<> 0 Cannot be zero>= 5 Greater than or equal to 5>= 0 And <= 100 Must be between 0 and 100 (inclusive)<= 0 Or <= 100 Must be less than 0 or greater than 100

(inclusive)>= Date ( ) Must be today’s date or later>= Date ( ) Or Is Null Must be today’s date or later or blank>= #1/1/96# And <#1/1/97# Must be a date in 1996Like "A????" Entry must contain 5 characters and start

with the letter A

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To write a validation rule, you can either write the rule yourself, or you can use the Expression Builder. To start the Expression Builder, click the Build button that appears when you select the Validation Rule Property.

The Expression Builder helps you to write expressions. It lists functions and operators that you can use. It can also prompt you to remind you what to do next and it will stop you making common mistakes.

Your Task

1. Write an Validation Rule and Validation Text to apply the following tests: Must be earlier than today’s date Must be between January 1st 1990 and today’s date

For Discussion

1. What would happen if you set these validation rules:

<= 0

>= 100

2. Why would you probably not want to set a validation rule for a text field?

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13. Keyboard Shortcuts

F2 Select an entire fieldCtrl+; Insert the Current DateCtrl+: Insert the Current TimeCtrl+Enter Insert a Line Break (use it in a memo or large text field)Ctrl++ Add New RecordCtrl+- Delete the Current RecordShift+Enter Save the RecordCtrl+Z Undo the last change you made (don't rely on this)Ctrl+Enter Open the selected object in Design ViewAlt+F4 Quit Access

14. Summary (from the Access Help file)

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Access1

Education

Transcript of Access1