- •2. Data, Information, knowledge
- •Flat file database model is a database that stores data in a plain text file. Each line of the text file holds one record, with fields separated by delimiters, such as commas or tabs.
- •Advantages
- •For every record in a child table (the “many” side), one and only one matching record must be in the parent table (the “one” side).
- •12. Designing the database
- •Specifying Field Data Types
- •Sorting records
- •Sorting by two or more fields
- •19. Filtering
- •22. Filters and Queries
- •Adding Selection Criteria
- •23. Performing Calculations in a Query
- •Using Aggregate calculations (Totals) in a Query
- •24. Parameter queries
- •25. Update queries
- •26.Make-table query
- •27. Three ways to arrange information for display or distribution
- •28. Record source can be
- •Creating Simple Forms with the Form Wizard
- •32. Creating a form in design view
- •33. The list of properties depends on current selection.
- •The easiest way to create an input mask is to use the Input Mask Wizard.
- •41. You can specify customized responses to user actions, such as clicking a button, opening a form, or selecting an option in an option group.
- •Events are grouped into eight categories, depending on the effects of the event. For example, some events relate to the data, others to filters, and still others to keyboard actions.
- •Associating the Macro with a Report Event
- •Some PivotTable Terms
- •Item – an element in a field.
- •To create a one-dimensional PivotTable that shows the data field details, you do the following:
- •Creating a PivotChart Report
22. Filters and Queries
Filters and select queries both retrieve a subset of records from a table or another query.
The results of both filters and queries can be used as the source of data for forms and reports.
You can also sort the results of both and save the sort order for use in a later work session.
Both methods let you edit the data displayed in the results, if editing is otherwise permitted.
As a rule, you use a filter to view or edit some records temporarily in a datasheet or form. If you want to return to the subset of records at a later time, you should use a query.
Queries are separate database objects that appear in the Navigation Pane, while a single filter is saved with a table.
If you use a query, you do not need to open the table first, because a query is an object in its own right. With a filter, you must open the table first before you can view the results of the filter or design a new filter.
You use a query if you want to extract data from multiple tables, control which fields to display, or perform calculations on field values. None of these operations is permitted with filters.
Adding Selection Criteria
The selection criteria in queries are expressions defining a condition that must be met for the record to be included in the subset. An expression is a combination of symbols, values, identifiers, and operators used for many purposes.
Symbols used in expressions include quotation marks, colons, asterisks, and other special characters. Values can be expressed as literal values, constants, the result of a function, or an identifier. Identifiers refer to the value of a field, a control in a form or report, or a property. An operator is a symbol or word that indicates an operation to be performed on one or more elements in the expression.
23. Performing Calculations in a Query
You can perform many types of calculations in a query that are recomputed each time the query is run, so you always have current data/ results of the calculations. In a query, two types of calculations can be used: aggregate calculations and custom calculated fields. The aggregate calculations are predefined operations performed on groups of records and provide :counts,averages, and other information about field values in all records or in groups of records. The custom calculated fields create new fields in a record by combining the values in other fields in the same record. You can create new Numeric, Date, or Text fields for each record using custom calculations. For example, use the expression [Delivery_Date] – [Order_Date] to create a new field Duration. Later you can use it to calculate the average duration of delivering order.
Using Aggregate calculations (Totals) in a Query
Sum -- used to add a column of numbers.
Average -- used to find the average of a column of numbers.
Maximum -- returns the highest value in a field.
Minimum -- returns the lowest value in a field.
Count -- used to count the number of same values in a query.
Summarizing all records To summarize field values in a query, start with a select query, add the field you want to summarize, and then specify the way you want the fields summarized. [Start a new Select Query and drag the field you want to the grid. On the Design tab’s Show / Hide group, click Totals command to add the Total row to the grid. Click the Total cell in the column and choose the function from the drop-down list option.]