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Introduction to Queries

Introduction to Queries. William Klingelsmith. Reminders. MyITLab Lesson C due 10/22 Homework #4 (Nielson TV Problem) due 10/26 Last day to drop is also 10/26 Midterm grades will be computed on HWK1-3 and Excel Exam. Database Updated.

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Introduction to Queries

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  1. Introduction to Queries William Klingelsmith

  2. Reminders • MyITLab Lesson C due 10/22 • Homework #4 (Nielson TV Problem) due 10/26 • Last day to drop is also 10/26 • Midterm grades will be computed on HWK1-3 and Excel Exam

  3. Database Updated • The Music database we worked on last class has been augmented with several records • Two new tables (Genres and Sales) need to be added to this database • These tables and their records are stored in external files

  4. Importing Data • To import data from external sources, you will utilize the External Data tab in Access. • There are many different import/export options, but today we will focus on XML file imports. • “XML File” in the Import & Link subgroup on the External Data Tab

  5. Importing Data • After you choose your file, you will get this dialog. • Most of the time for this class, the default ‘Structure and Data’ is appropriate.

  6. Establish Relationships • Now that we have all of our tables, we must link them together using relationships • Albums -> Songs • Albums -> Sales • Use Referential Integrity • What about the link between Genre and Albums?

  7. Lookup Fields • Lookup fields are special Data Types in tables. • Possible choices for a field in one table are determined by existing entries in another table. • They let you make a dropdown type box for a field which can aide in data entry efficiency. • They will build a relationship between two tables automatically.

  8. Lookup Fields • Move to the design view of the Albums table • Change the data type for the Genre field to Lookup Wizard • Follow the wizard’s instructions to create the lookup field. • When finished, the wizard should create a relationship between the Genre and Albums tables.

  9. Queries • Queries are used to view a subset of the data contained in your database • These subsets are most commonly broken down by a limiting criteria • “Return only the songs that are on albums by a particular artist” • “List all albums of a certain genre” • Think of QUEries as QUEstions!

  10. Constructing a Query • Let’s start our query lesson with a simple example • We wish to list every Artist and Song name • Where is this information stored?

  11. Constructing a Query • Move to the Create tab and choose Query Design • The Show Table dialog lets you add relevant tables to your query • Choose only Songs for this query

  12. Constructing a Query • Field: Name of the field • Table: Table the field belongs to • Sort: Sorting the results in Ascending/Descending order • Show: Hide/Display the result in the query • Criteria and Or: Allows you to narrow filter results of the query on some criteria

  13. Running a Query • Queries can be executed in two ways • The Run button in the design view of a query • Switching to the Datasheet view of a query

  14. Adding Criteria • Save the last query as Query A • Duplicate it in the object pane • Call the copy Query B • Open the design view of Query B • For this query, we wish to only return the songs performed by the artist ‘Venetian Snares’ • In the criteria row under the Artist field type “Venetian Snares” • Run the query

  15. Criteria Notes • Criteria across multiple fields on the same line are all used at once (AND) • Multiple criteria under the same field are all acceptable choices (OR) • Conditional operators (<, >, <=, >=, etc) can be used in criteria • Access has two wildcard operators (? And *)

  16. Criteria Examples (OR) • Duplicate Query B and call it Query C • On the row below where “Venetian Snares” currently resides, type “Fleet Foxes” • Notice that songs from both artists are now returned in the result • Criteria is OR’d • It is saying that results can be either from Venetian Snares OR Fleet Foxes

  17. Criteria Examples (AND) • Duplicate the last query and call it Query D • Add the Favorite field from the Songs table to your query design • Criteria should be as follows: • Artist: Venetian Snares • Favorite: Yes • We have fewer results than before • Criteria across multiple fields on the same row are AND’d • “Songs must both be by Venetian Snares and a favorite to be included in the query”

  18. Criteria Examples (Conditional Operators) • Let’s try to get a list of all albums released before the year 2000 • Create a new query and add the Songs and Albums tables • Populate the query with the fields: Artist, SongName, AlbumName, Genre, ReleaseDate • In the criteria under the release date enter: “<1/1/2000”

  19. Criteria Examples (Wildcards) • Wildcards are operators that can be substituted for a set of characters • * Operator allows any set of characters of any length • Let’s say we had a field that held first names. By using S* in the criteria, we could get these results from our query • Sara • Stephen • Sue • ? Operator allows any set of characters of length 1 • By using ?ill we could get results such as: • Will • Bill • Jill

  20. Criteria Examples (Wildcards) • Return only Albums that begin with the letter T

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