Calculated fields

A calculated field is a "virtual field" in a query. The field is virtual in the sense that it is not stored anywhere in the database. Instead, it is calculated dynamically when the query is used. Learning objectives: create a calculated field; understand why ACCESS add square; brackets around field names; understand the use of the ampersand operator (&). (pdf file, install Acrobat Reader to read this tutorial)

Related Tutorials

Create a Calculated Field with the Expression Builder
This tutorial will introduce calculated fields in MS Access. We can use calculated fields both in queries and tables; here, we will focus upon their creation and use in general. This lesson will include: A brief introduction to calculated fields; An introduction to the MS Access Expression Builder; A practical walkthrough of the process of creating a calculated field.

Calculated fields misinterpreted
Unlike fields in a table, there is no way to specify the data type for calculated fields. If your data sorts incorrectly, or the wrong records are returned, Access is probably treating your calculated numeric or date field as text.

Create a calculated control
You can use calculated controls to display the results of a calculation. For example, if you have a report that displays the number of items sold and the price of each unit, you can add a calculated text box that multiplies those two fields to display the total price. The Control Source property of the calculated text box contains an expression (expression: Any combination of mathematical or logical operators, constants, functions, and names of fields, controls, and properties that evaluates to a single value. Expressions can perform calculations, manipulate characters, or test data.) that multiplies two fields (the number of items times the unit price) to obtain the result. What do you want to do?: Create a calculated control, Change a bound control to a calculated control, Learn which types of controls can be calculated controls.

Calculated Fields
How do you get Access to store the result of a calculation? For example, if you have fields named Quantity and UnitPrice, how do you get Access to write Quantity * UnitPrice to another field called Amount?

Queries
This tutorial covers: Types of queries, Creating a query, The Design view, Adding fields, Defining calculated fields, Forming expressions, Column headings, Changing the order of the fields, Saving the query, Running the query, Modifying the query design, Ordering rows, Selecting rows, Conditions ,Multitable queries, Joining tables and The external join

A handy tip on Concatenation, or Combining Microsoft Access data
Use the plus sign '+' when creating a calculated field where you want Null returned if a field isn't filled in. For example, if your table contains FirstName, LastName, and MiddleInitial fields and you would like to make the Full Name display in a query for a report.

Unbound/Bound Forms
I have inherited a database that is used to track product development. It is set-up so that one product has one key(product_id). The bosses have asked to be able to track the changes to the product over the development life cycle. I have created a table with the following fields: product_id, change_id, change_notes, and change_status. I have created a form that holds all of these fields, and two unbound boxes. One of the boxes contains an expression that is fed by the product_id from the open form, and the other (to create a change_id) is created by adding a "C" and a now() after the product_id (product_id & "c" & now()). Problem: I am having an issue getting the unbound boxes to populate the product_id and change_id field in the actual table when I try and save. I am really at a loss. Have been googling calculated fields and before update for the last couple of hours...

Sort a form's records based on the value of a calculated field
In Access 2003/XP/2000/97, I have a calculated field on a form which displays the number of records in the Account_units table for the account currently displayed in the Account form.

Managing Data Fields
So far, to get acquainted with database fields, we have used two techniques of creating a table and some techniques of adding fields to a form. One of the techniques we used, the Datasheet View, provides a very simplistic way. The Datasheet View is mainly used to perform data entry or to test some fields. It has so many limitations that you will hardly use it. For example, you cannot control or customize the behavior of fields if you create the table in Datasheet View. The other technique we used, the Table Wizard, allows you to use some already created and customized fields. For one thing, you would not know what exactly those fields are configured to do and whether they can control data entered in them. For another thing, if you do not like the way they behave, you would have to modify the configuration that was already done. This is why you should know how to design your tables. TOC: Table Design and Fields, Queries and Fields.

Data Fields on Forms and Reports
As we saw in previous lessons, fields are created on a table, then they can be added to a query. Based on the way Microsoft Access deals with fields, a field on a table cannot be created as a combination of other fields, as if it were an expression .

Searching 6 fields all optional
Hi, Could you possibly help with this... ? I have a second problem which I would love to get some help on, I've hit a brick wall with it. I have a form which has 6 search fields on it. They are used to search for data in the "applicants" form. They are: First Name Last Name Company Post Code Telephone Number Applicant ref I want the user to be able to search on 1 or more or all fields. I appreciate that if the data in one of those fieds is invalid and does not appear in a record then it will not show the resulting record. Although if they enter 3 fields with correct data to minimise returned records to a more accurate set BUT they leave the other 3 fields blank, then I need the query to ignore the blank fields.

Controlling the visibility property of a picture
I am using Access 2003. I have a simple checklist form that contains several YES/NO data type fields and a picture. I would like to make the picture visible when ALL of the fields have a YES value (boxes checked) (and keep the picture hidden when any one of the fields is set to NO.) The default value for the data fields is NO. Can you tell me how to code this or point me to an example to use?

Truncation of Memo fields
In Access tables, Text fields are limited to 255 characters, but Memo fields can handle 64,000 characters (about 8 pages of single-spaced text) - even more programmatically. So why do memo fields sometimes get cut off?Identifies the reasons why Memo fields may be truncated after 255 characters in queries or exports in Microsoft Access.

Edit a calculated field in PivotTable view
Learn how to edit a calculated field in PivotTable view.

Downlaod tutorials
Download the following tutorials in pdf file format: Introduction to Access, Tables, Foreign keys, Relationships, Importing and linking, ODBC, Basic QBE, Calculated fields, Basic SQL, Forms, Subforms, Bound controls, Parameter queries, Action queries, Visual Basic, Event-driven programming, Shipments, Backorders, Data warehousing, OLAP, HTML, HTML forms, Server-side scripting, Sessions, ADO, Business objects

StLinkCriteria - 2 fields
I'm building an Event at Access to visualize a report (called Carttoes) linked to the data of two fields: [codigorodada] and [caixas]. I only know how to set the linking criteria for one field, how could I put the StLinkCriteria for both fields? ...

Data Field Design
As a database is expanding, so are its objects. For example, many of the tables created by the Database Wizard lack some fields that otherwise would not suit a particular scenario. As we learned already, you can add new fields to a table. Since such new fields are not added to the corresponding forms or reports, you have to insert these fields in the appropriate objects. Even though the Form Wizard or the Report Wizard can be used to create quick objects, you still have the option of changing or improving their look by moving fields around and changing the sequence of fields' navigation. Learn: Fields Design Techniques, Form and Report Design Accessories, Forms, Reports, and Data Existing Fields, Forms, Reports, and Queries Fields, Form and Report Design: Controls Insertion, Form and Report Design: Controls Selection, Form and Report Design: Controls Moving, Form and Report Design: Controls and Sections Sizing, Form and Report Design: Controls Deletion, Tab Order, Opening an "Un-Openable" Form.

Introduction to Expressions and Operations
The data fields we have used so far were created in tables and then made available to other objects (forms and reports), so those objects can implement their own functionality without worrying about displaying empty or insignificant fields. In various scenarios, you will need to display a field that is a combination of other fields. For example, you may need to combine a first name to a last name fields in order to create a full name field, or, to calculate an employee’s weekly salary, you may need to retrieve the value of a Salary field and multiply it with the value of a total number of hours worked in a week.

Add a field to a table
Tables, the basic building blocks of a database, are made up of records (sometimes called rows) and fields (sometimes called columns). For example, a contacts table would contain several records, and each record would contain several fields that store information, such as the last name, first name, telephone number, and city of each contact. This article explains why well-designed fields are important and shows you several basic ways to add fields to a table in Microsoft Office Access 2007.

Avoid multiple database fields that contain similar data in Access
When designing tables in Microsoft Access, you should avoid creating multiple fields that repeat the same kind of data. If a table stores the same kind of data in more than one field, it's hard to search for a particular piece of data because it could be in any of the fields. In addition, it's difficult to sort data and do calculations because you might need to include data from several fields to get accurate results.

Create an Index to Sort Records Faster
Access uses an index in the same way that you would use an index in a book: to find information more quickly. Indexing fields that you frequently search can speed up sorts. You can index multiple fields or single fields. These instructions are for Access 97.

Data Editing and Security Issues
Data Entry and Editing is a major activity for maintaining the information up-to-date in databases, before we are able to prepare any meaningful output for human consumption. It is important that we make these tasks easier to the User by providing Combo Boxes, Check Boxes or Calculated Fields, like Payment-Due-Date after 30 days of Material-Delivery-Date and so on. Another important aspect is data security. I am not referring to the protection against unauthorized access from outside, for which we have adequate built-in MS-Access Security features that can be put to use. Here, our emphasis is on unintentional changes or deletions of important information by Authorized Users.

Examples of query criteria
When you want to limit the results of a query based on the values in a field, you use query criteria. A query criterion is an expression that Access compares to query field values to determine whether to include the record that contains each value. In this topic: * Introduction to query criteria * Criteria for Text, Memo, and Hyperlink fields * Criteria for Number, Currency, and AutoNumber fields * Criteria for Date/Time fields * Criteria for other fields

Too Many Fields Defined in a Microsoft Access Database Table
Ever received the "Too Many Fields Defined" Error message when saving your database table? Microsoft Access keeps an internal count of the total number of fields in a database table and has a limit of 255 fields per table.

Database Fields on Forms and Reports
As we saw in previous lessons, fields are created on a table, then they can be added to a query. Based on the way Microsoft Access deals with fields, a field on a table cannot be created as a combination of other fields, as if it were an expression (unless the field is created as lookup�). Instead, the fields on a table are primarily created to store data. On the other hand, as we will see in the next few lessons, a new field can be added to a query as a combination, through an expression, of other fields. Forms and reports present this same solution. Besides using the fields of a table or a query, a new field can be added to a form or report. This is because forms and reports make use of objects called Windows controls. In other words, the fields of a form or a report are created from Windows controls. Learn: Labels, Text Boxes, Combo Boxes, Navigation Buttons, Forms Fields, Subform, Record Selector, Reports and Controls, Subreport, Common Field Design on Forms and Reports, Introduction to Form Design, Introduction to Report Design

Sorting and Filtering Text-Based Fields
In reality, queries are not the only objects used to analyze data. The main reason for using a query is that it can save its results to be used when necessary. The analysis done on a table or a form is usually temporary and may be lost when you close the table or the form. Other than that, most data analysis operations you can perform on a query are also available on tables and forms. TOC: Sorting Records on Empty Fields, Filtering Empty Fields, Sorting String-Based Fields, Sorting Records in SQL, Filtering String-Based Fields

Why I stopped using Yes/No fields
A workaround for a bug where Microsoft Access crashes or fails to execute queries with Yes/No fields.

Delete Fields From a Table
Access 2003 can appear daunting when attempting to change or work with database fields and tables. By following this easy tutorial you will be able to delete fields from a table in Access 2003.

Add Fields to a Table
Access 2003 can appear to be a very confusing and frustrating program to run, requiring multiple tables and views to use properly. Adding fields will often require you to use both Design View� and Datasheet View.� The following steps will help you to add fields to a table in Access 2003.

Introduction to the Records of a Table
After creating a table, you (actually the user) can start(s) populating it with information. Data entry consists of entering data into the database. To do this, you can use a table or some of the other objects we will study. Data is entered in a table by typing it into cells. Some fields can be configured to accept some types of data and reject others. Some other fields would allow anything. This depends on how the database fields were setup.

How to Add Fields to a Microsoft Access Table
When you created your Access table, you entered the fields you wanted at that time. But later you might realize that you need one or more new fields. Say, for example, you made a database of friends' addresses, but didn't include a field for a middle initial. Then you get two friends with the same name. Uh oh. Add a field. These instructions work for Access 97.

Select fields and records
Learn: Select fields and records in a datasheet, Select fields and records in a data access page.

Concatenate two fields in a query in Access 2003
In Access 2003/XP/2000/97, I have a database and I need to know how to concatenate two fields when creating a query. I need to be able to see these two concatenated fields in my query result set.

Multivalued Fields
Multivalued fields in Microsoft Access offer you the opportunity to allow users to select one or more options for a field value by using checkboxes.

Working with Database Fields
Microsoft Access database fields are created by entering a field name and a field data type in each row of the field entry area of the database table window. The field description is an option to identify the fields purpose; it appears in the status bar during data entry. After you enter each field's name and data type, you can specify how each field is used by entering properties in the property area. Before you enter any properties, however, you should enter all of you fields names and data types.

Tables and Queries Aesthetics
When examining records on a database, some tables are so wide the user would need to scroll left and right to see fields one screen at a time. Sometimes, the user does not need to see all fields all the time. Microsoft Access allows you to temporarily hide unneeded columns. This feature does not delete records or columns; it only hides them and can display the columns as needed. Topcis: Columns and Fields Visibility, Table and Query Datasheet Formatting

Concatenate two fields in a query in Access 2007
In Access 2007, I have a database and I need to know how to concatenate two fields when creating a query. I need to be able to see these two concatenated fields in my query result set.

How to Change the Order of Fields in a Table
When making an Access 2003 datasheet, there are going to be times when you need to change the order that the fields are arranged. Follow the simple tutorial to change the order of fields in an existing table in Access 2003.

Calculated fields

View Tutorial