Microsoft Access – Tutorial 3 Querying a Database a query is a question you ask about data stored in a database you tell Access what fields you need and what criteria Access should use to select the records ex. find records for employers located in a specific State or Province queries allow you to: display selected fields and records from a table sort records perform calculations generate data for forms, reports and other queries update data in the tables in a database find and display data from two or more tables

Microsoft Access – Tutorial 3 Query by Example (QBE) You Query by Example by giving Access an example of the information we are requesting Access then retrieves the information we are requesting We want to create a query to display: employer ID employer name city contact first name contact last name web site information for each record in the Employer table

Microsoft Access – Tutorial 3 Query by Example (QBE) open the Northeast database we created last week (I have included a copy in the Common Directory on the desktop) Click Create > Query Design show the Employer Table and the close the Show Table dialog box maximize the Query window

Microsoft Access – Tutorial 3 Query by Example (QBE) you will see the field list in a box entitled Employer (the table name) you can double-click or drag fields to the design grid in the design grid, you include the fields and record selection criteria for the information that you want to see you can see the current results of your query at any time by View button or the Run button on the top left the current results will appear in a datasheet view

Microsoft Access – Tutorial 3 Query by Example (QBE) drag the split bar and resize the windows as you like double-click the following fields in order: EmployerID, EmpoyerName, City, ContactFirstName, ContactLastName and Website note the checkbox that that allows you to show or hide fields click Run (or View (Datasheet View)) to see the results in a datasheet click the View button to return to Design View click the Save button on the toolbar and name the query EmployerAnalysis

Microsoft Access – Tutorial 3 Updating Data using a Query return to the Datasheet view indicate that The Adele Bannister House (10135) now has a website change the Contact person for Alpine Touring Center (10152) to Mary Grant close the Query and note that it has been added to the Queries in the Objects bar open the Employers table and verify that the changes have been made close the Employers table

Microsoft Access – Tutorial 3 Table Relationships remember that Access is a relational database management system relationships are created among tables by using common fields this process is often called a join when you join tables with a common field, you can extract data from them as if they were one table the Employer and Position tables will be joined with the common field EmployerID (a foreign key) you can use a query form or report to extract selected data from each table even though the information is in two tables

Microsoft Access – Tutorial 3 One-to-Many Relationships a one-to-many relationship exists between two tables when one record in the first table matches zero, one or many records in the related table and when one record in the in the second table matches exactly one record in the first table the primary table is the one table in the one-to-many relationship this is the Employer table the related table is the many table this is the Position table

Microsoft Access – Tutorial 3 One-to-Many Relationships orphaned records can be created when inconsistencies occur between tables for example: if an Employer ID is changed in the Employer table if an Employer is deleted from the Employer table if a position is added for an Employer that doesn’t exist in the Employer table

Microsoft Access – Tutorial 3 One-to-Many Relationships Referential Integrity is a set of rules that Access uses to prevent records from being orphaned it maintains consistency between tables when you update data when you add a record to a related table, a matching record must already exist in the primary table if you attempt to change the value of a primary key in the primary table, Access prevents the change if matching records exist in a related table (however, if the cascade updates option is chosen, the foreing key values will be updated automatically) Access prevents the deletion of records in a primary table if matching records exist in a related table (if cascade deletes option is selected all records with that key will be deleted – this is not recommended)

Microsoft Access – Tutorial 3 Defining Relationships you can define relationships between tables using the Relationships window Database Tools > Relationships add Employer and Position and close the Show Table dialog box lengthen and widen each window to show all fields click and drag EmployerID from the Employer Table to EmployerID in the Position table the Edit Relationships window will appear the Primary Table, Related Table and Common Field will be visible

Microsoft Access – Tutorial 3 Defining Relationships check Enforce Referential Integrity note that the two Cascade options become available check Cascade Update Related Fields (remember that it is not recommended to check the Cascade Delete Related Records as you may inadvertently delete records) click create and note the join line that appears and the symbols on it now create a one-to-many relationship between the NAICS table and Employer Table with NAICS code as the common field (foreign key) click the Save button and Close the window

Microsoft Access – Tutorial 3 Multi-Table Queries now that we have created Relationships among (joined) our tables, we can query them as one create a new query in design view add the Employer and Position tables create a query in the following order: EmployerName City StateProv Openings PositionTitle StartDate EndDate run it and save the query as EmployerPositions

Microsoft Access – Tutorial 3 Sorting Data in a Query sorting is rearranging records in a specified order or sequence open the EmployerPositions query in datasheet view select the first record in the Employer Name field and use the sort buttons (drop-down arrows on column heading) to sort alphabetically to sort by more than one field go to Design View select the entire column for Openings click and drag it so that it is the last field (after EndDate) use the Sort field to sort PositionTitle Ascending sort Openings Descending run the query within groups of fields with the same Position Title, the record sorts the number of openings from highest to lowest save the query

Microsoft Access – Tutorial 3 Filtering Data in a Query you can filter query results using the Filter by Selection button double-click the word clerk in one of the Position Title records click the Filter by Selection button (located in Home > Sort and Filter group > selection) you will see only results for different kinds of clerks click the toggle filter button to turn off the filter filter results for New Hampshire (NH) Untoggle the filter and close the query

Microsoft Access – Tutorial 3 Defining Record Selection Criteria you can specify a condition which is a criteria or rule that tells Access which records to display we will Create > Query Wizard using a condition click Simple Query Wizard and make sure the Table: Position is selected add all the fields by clicking >> remove both PositionID and EmployerID from the Selected Fields list box to add fields from another table after the current set of fields, select Openings now add EmployerName, StateProv, ContactFirstName, ContactLastName and Phone from the Employer Table

Microsoft Access – Tutorial 3 Defining Record Selection Criteria click the Next button make sure the Detail radio button is selected and click Next again name the Query HousekeepingPositions and click the Modify the Query Design radio button and click Finish in the PositionTitle Criteria type housekeeping Access adds “ signs before and after the criteria run and save the query only housekeeping positions will be displayed

Microsoft Access – Tutorial 3 Formatting the Appearance of the sheet select all the records Home > Font Size (in the Font group) change the size of the fonts to 8 double click between columns to resize them

Microsoft Access – Tutorial 3 Setting Range Criteria open the HousekeepingPositions query in Design View remove the PositionTitle criteria set the Wage criteria >=17 run the query and Save (Office Button > Save As) it As HighWageAmounts

Microsoft Access – Tutorial 3 Using Multiple Selection Criteria with the And operator open the HousekeepingPositions query in Design View add MA as criteria for StateProv run the Query and you’ll see results that match both criteria close and save the query right click on the Query July1Positions in the Query window rename it MAJuly1Positions

Microsoft Access – Tutorial 3 Using Multiple Selection Criteria with the Or operator create a new query in Design view use the Employer and Position tables and add the following fields: EmployerName, City, PositionTitle, HoursPerWeek, and Experience set the HoursPerWeek criteria to <30 in order to select records in which either (not both) of the conditions is met type Yes in the or: field run the query sort it alphabetically ascending by Employer Name Save it as HoursorExperience