Microsoft Access. Introduction

Transcription

1 Microsoft Access Introduction Starting Access Access is an interactive, relational database management system. A database is an organised collection of data stored in categories that are accessible in a logical or practical manner. Relational databases enable data to be stored in multiple tables linked together via data indexes. This makes working with the data faster and easier. Once entered into the database, the data may be manipulated or viewed in various ways such as by sorting or by specially set-up queries and reports. To start Access, click the Public button on the taskbar, and choose Access from the MS Office option: After the initial start-up screen, the Access start-up window should appear like this: This is a standard application window with a title bar at the top containing the minimise and maximise buttons in the right corner. Microsoft Access 5-1

2 The Menus Floating Menus Toolbar Creating A Database Below the title bar, is the menu bar with several of the usual Windows menus including File, View, Edit and Help. As you perform different tasks in your session the menu and toolbars will change to display menus and options applicable to each situation. The initial menu options are as follows. The File menu allows you to create, open or close databases, create or rename objects associated with databases, to import or export data and to print items. The Edit menu is a standard Windows menu from which you can copy, paste and delete information and define relationships between data. The View menu can be used to specify the object you wish to see and the style in which it is to be displayed. You can also choose the style of the toolbars and set certain options. The Insert menu provides an easy way to create any of the database objects you may need to use such as tables and forms. The Tools menu contains utilities for autocorrecting text and setting database security and encryption. You can also set up macros containing combinations of commonly used procedures from here. The Window menu allows you to arrange the way in which the various open windows are positioned on the screen. The Help menu offers three ways of obtaining on-line help. You can call up the Office Assistant utility, see the contents of the Access Help system or use the What's This? feature to point to an object and see a description of it. In addition to the normal menus, clicking the right mouse button whilst the cursor is over an object produces a floating menu with several of the more commonly used menu options. You may find this method faster to use. Below the menu bar is the toolbar. Only three buttons on the toolbar can be used at this stage. One to create a database, one to open an existing database and one on the far right which can be used to obtain help. Many of the menu commands are duplicated in the toolbar. In addition to the help system, pointing to any button in the toolbar will produce a pop-up label to describe the function of the button. There is also a status bar at the bottom left of the screen that will display information relevant to the current activity. To create a database, choose New Database from the File menu or click on the new database button in the toolbar and the following window appears: 5-2 Microsoft Access

3 As the Blank Database icon is already highlighted, just click on OK to produce the next dialogue box: Type the name of the new database in the File Name box or accept the default already supplied. The name will have the extension.mdb added automatically. Make sure the correct drive (G: or A:) and folder are selected in the Save in box by selecting from the drop down list visible when you click on the downward arrow to the right of the box, then click on the Create button. The menus and tool bar of the Access window change and a Database Window appears: The Database Window contains three main buttons, New, Open and Design, along with a series of Object tabs along the top. Microsoft Access 5-3

4 Objects Tables Creating a Table Every database can contain several types of object. The data itself is contained in an object called a table. The data can be used in a wide variety of formats, for example, mailing lists, forms, reports and graphs. Each of these is a type of object. You create objects by clicking on the appropriate tab in the Database window, then clicking on the New button. Once objects such as tables have been created, they will be listed under the object tab whenever it is selected. To open an existing object, click on its name so that it becomes highlighted then click on Open. All objects have properties that can be set to determine how the object appears or operates. A table is the first type of object to create in a database. It is a way of defining how the data is to be stored. As with all databases, a table consists of records (rows) and fields (columns). Each record represents one individual item in the database, such as a person in an address book, and each field represents a component of the record such as a surname or part of an address. Access is a relational database management system. This means that instead of having the data stored in one large file or table, it can be divided into several smaller tables. This reduces the amount of duplication of data and makes it easier to manage. The tables can be related to each other by a common field such as a case identification number. You can work with several tables at the same time. To create a table, make sure that the Tables object tab is selected then click on the New button. This presents you with a dialogue box with five choices: If you select TableWizard, Access will help you to create a standard table by using pre-defined fields. Selecting Design View, on the other hand allows you to design your own table. 5-4 Microsoft Access

5 Select Design View and click OK to bring up the Table design window: Field Names and Data Types Primary Keys Entering Data In the lower right corner of this window is an area containing a brief explanation of the section containing the cursor. Each field of the table has three components: the Field Name, which identifies the data stored in the field, the Data Type, which tells Access what kind of data will be stored in the field, such as text, numbers or dates, and the Description, which helps the user remember the purpose of the field. It is very important to choose the right data type for a field at this stage. Access will automatically insert a data type when you name a field but if you need to change it, click on the data type box, then click on the downward arrow that appears to the right of the box. You can then choose a new data type from the drop-down list. As you type in the name of each field, a Properties section appears in the lower left corner of the window where you can optionally define several properties for each field. Here you can specify the format of the data to be entered and specify criteria for validating the data as it is entered. When you have defined the name, data type and properties of each field, save the table by choosing Save from the File menu. At this point you will be informed that a Primary key has not been set and you will be asked if you wish Access to create one. A Primary key field is a field that is used uniquely to identify each record. The field can be used by Access to manipulate data more efficiently. You do not have to specify a key. If you wish to use one, you can choose an existing field or, if you answer yes to the prompt for Access to create a Primary key, Access will create an extra field containing an ID number for each case. Once you have defined the structure of a table, you can start to enter data into it. You created the table in Design view. To enter data, switch to Datasheet view by selecting Datasheet from the View menu. This produces a spreadsheet style window with the name of each field at the top of a column: Microsoft Access 5-5

6 Saving Data Finding Data Filters The highlighted box or cell of the datasheet denotes the insertion point for data. If you requested Access to create a Primary key, the first cell is a counter called ID, which is automatically filled in by Access. Press TAB to move to the next cell containing your first field. To add a record, just type in the appropriate data for the cell then press the TAB key to move to the next field. At the end of each record, pressing TAB will move down to the next record. You do not have to do anything special to save the data. When you leave a record to go to the next one or close the table, Access automatically saves any changes. To close the table choose Close from the File menu. The simplest way to find a record in a table is: From the database window, open the table in Datasheet view. Select the field to search by clicking on its name box. Choose Find from the Edit menu. Enter the value you want to search for in the Find What? box and click on Find First. You can also specify whether the search should match for case, in which direction to search and whether to search other fields. When you initiate a search, the cursor moves to the first occurrence of the search string in the table and the string is highlighted. To search for another occurrence of the same value, use the Find Next button. Using Find will only display one occurrence of a search value at a time. To find all records with a field containing a certain value, use a filter. For example, you could use a filter to select all people from a particular town in an address book database. To create a simple filter: Open the table from the database window Move to the column on which you want to use a filter and click on a cell containing the value that you are interested in. Choose Filter by selection from the Record menu The result is a list of only those records, that contain the same value as the cell you highlighted. You can also create a Form Filter that allows for more than one criterion to be used. To do this: Open the table. Choose Filter by Form from the Filter option in the Records menu. Click one of the fields then, from the drop down menu, choose one of the values that the record must contain to pass the filter. 5-6 Microsoft Access

7 To perform several filters and sort functions at the same time use the advanced filter option: Open the table from the database window. Choose Advanced Filter/Sort from the Filter option in the Records menu. This will open a Filter window in which you can define the records you want to see. Click on the required field listed in the upper part of the window and drag it down to the first Field cell in the lower part of the Filter window. Or double click on it to copy it automatically. Specify search criteria by typing the required value in the first Criteria cell. To apply the filter, choose Apply Filter/Sort from the Filter menu. The required records will be displayed in a datasheet view. For example, if you wanted to see all the records of people from an address database living in London and there was a field in the table called Town, place the Town field in the Field cell then type London in the criteria cell. The Filter window would like this: Sorting Remember that you can specify any number of fields using this method. By default, Access displays the table data in the order in which it was entered. You can sort an entire table by opening it and using the Sort option from the Records menu. You can choose an ascending or descending sort. Retrieving Data - Queries. You can also use the Filter window to produce a sorted listing of filtered records by clicking on the Sort Cell in the Filter window and choosing the required sort from the drop down menu. Queries enable you to gather data from fields in tables, create and calculate new fields and summarise data. They are similar to filters except that they can access fields in more than one table at a time. To set a query: Open the database you want to work on Click on the Queries tab in the Database window Click on New. Just as when creating a table, you are given a choice of using a wizard tool to create a standard query or choosing Design View to design the query from scratch. Select Design View to display the Show Table dialogue box. Microsoft Access 5-7

8 Specifying Criteria Forms Select the table or tables to be used by the query, clicking Add after selecting each one. Close the Show Table dialogue box to reveal the Query window. The Query window is very like the Filter window described earlier. Specify which fields and records you want to retrieve from the table(s) by pointing to the field name in the Table window and dragging it to a Field cell in the lower part of the Query window. Save the Query and name it using Save from the File menu. Choose Run from the Query menu to activate the query. The fields specified in the query are displayed for each record in the database. The set of records resulting from a query is called a dynaset. You can select as many fields as you wish for the query. Each time you select one, the check boxes in the Show cells are checked meaning that the data in the fields will be displayed when the query is executed. You can vary which fields are displayed by unchecking any of these boxes. If you want to restrict the records displayed by a query to those in which a specified field contains a certain value, use the Criteria cells of the Query window just as in the Filter window described earlier. You can add and combine criteria in the Query window to create powerful searches to meet exacting conditions. To modify a query, choose Design View from the View menu or click on the Design View button. You can control the way in which data is displayed by creating another type of object called a form. To create a form: Click on the Forms tab in the Database window. Choose New and Design View. (Once again, you can use the FormWizard and choose Autoform to let Access provide you with a ready-made form if you prefer). Type in the name of a table or query you wish to view or select it from the list under the down arrow to the right of the cursor. Choose Field List from the View menu to display a list of fields. Drag the required fields to a position on the form. Save and name the form using Save from the File menu. You can also create a form by selecting a table from the Database window then clicking the AutoForm button on the toolbar. Once the form has been created, you can use it to view, change, add and delete records in the table. To move from record to record, use the navigation buttons in the corner of the Form window or use the Go To command in the Records menu Forms are convenient when you want to view all the fields of a single record on the screen. You can switch between Form view and the original Datasheet view using the View menu or the appropriate buttons in the tool bar. 5-8 Microsoft Access

9 Reports Macros Modules Linking and Importing Data Closing and Exiting To add records using a form, choose the Forms tab in the Database window then select the form by name. A blank form appears awaiting data. Press TAB to move between fields and continue entering the data. At the end of the form, pressing the TAB key will save the data just entered and take you to another blank form. A report is another type of object much like a form but with greater flexibility and control when printing data including various ways of producing summary information. A macro is an object used to automate a list of actions. For example, you might want a set of forms opened automatically when a database is opened. Macros can be used in a variety of places, for example, attached to a form, a report or a menu command. Access contains its own programming language, Access Basic, which can be used to automate more complex processes than macros can handle. A module is an object containing Basic procedures. There are two ways of using data that is already stored in computer form. Firstly, data from different file types such as spreadsheets and text files can be imported into an Access table. In this case the data is copied from the original file into the table. To import data: Open the database. Choose Get External Data, Import from the File menu. Select the location, the type of data and the specific file in the Import dialogue box. Click on the Import button. Alternatively, you can view and update data stored in another database or in a file from another package such as Excel or Paradox without copying or moving the data. To do this, you link the file to the current database. The original file format is unchanged. To link a file: Open the database. Choose Get External Link from the File menu. Select the location, the type of data and the specific file in the Link dialogue box. Click on the Link button. Respond to any further dialogue boxes that appear for example, to select particular data sets from the selected files. Note that in the case of linked data, you may not be able save any changes you make, depending on what access rights you have to the original file. When you have finished working with a database, choose Close Database from the File menu. You may then open another database or if you have finished your Access session, choose Exit from the File menu. Microsoft Access 5-9

10 Subsequent Access Sessions When you start an Access session after having worked with a database previously, the initial startup process is slightly different. On start-up, you will see the following dialogue box giving you the option to start a new database, use the database wizard or open previously saved databases: Check the appropriate option and click OK Microsoft Access