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Day 16: Access Chapter 2

Day 16: Access Chapter 2. Tazin Afrin Tazin.Afrin@mail.wvu.edu October 10 , 2013. objectives. Single table query Multi-table query. Single table queries. Which customer currently has a balance over $5000? Create a query

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Day 16: Access Chapter 2

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  1. Day 16:Access Chapter 2 Tazin AfrinTazin.Afrin@mail.wvu.edu October 10, 2013

  2. objectives • Single table query • Multi-table query

  3. Single table queries • Which customer currently has a balance over $5000? • Create a query • A query enables you to ask questions about the data stored in a database. • Need reference of table • For previous question refer Account table

  4. Query design view • Query Design view enables you to create queries; the Design view is divided into two parts – • the top portion displays the tables • the bottom portion (known as the query design grid) displays the fields and the criteria.

  5. Single table query • Create in two ways – • Simple query wizard: • provides dialog boxes to guide you through the query design process. • helpful for users who are not experienced. • Query design tool: • For more advanced users • Provides the most flexibility

  6. Query datasheet • Display the results of the query. • Query’s datasheet looks and acts like a table’s datasheet • Usually a subset of the records from the table. • Only shows the records that match the criteria. • Allows you to enter a new record, modify an existing record, or delete a record. • Any changes made in Datasheet view are reflected in the underlying table. • Caution: Changes Made to Query Results Overwrite Table Data

  7. Single – table select query • A select query displays only the records that match the criteria entered in Design view. • Create -> Queries -> Query Design • Show Table Dialog Box appears • Select table • Add query

  8. Use query design view • Consists of two parts: • The top portion contains tables with their respective field names. • The bottom portion (known as the query design grid) contains columns and rows. • Field row • Table row • Sort row • Show row • Criteria row

  9. wildcard • A wildcard is a special character that can represent one or more characters in the criterion of a query. • * mark • Represents one or more characters • If name start with Smsearch by Sm* • S*ndwill return Sand, Stand, or StoryLand. • ? mark • Stand for a single character • H?ll will return Hull, Hill, or Hall etc.

  10. Comparison operators • A comparison operator can be used in the criteria of a query. • Such as – • equal (=) • not equal (<>), • greater than (>) • less than (<) • greater than or equal to (>=) • and less than or equal to (<=) • Query for salary >5000

  11. Null • Null is the term Access uses todescribe a blank field. • Example: • Is Null • For an Employee field in the Customers table when the customer has not been assigned a sales representative. • Is Not Null • For the ShipDate field; a value inserted indicates the order was shipped to the customer.

  12. Establish Logical criteria • The AND logical operator returns only records that meet all criteria. • The OR logical operator returns records meeting any of the specified criteria. • The NOT logical operator returns all records except the specified criteria.

  13. Query operation • Copy a query • Run a query

  14. Multi-table query • A multi-table querycontains two or more tables. • Enables you to take advantage of the relationships that have been set in your database. • Related tables should already be established when you create a multi-table query. • Related tables are tables that are joined in a relationship using a common field.

  15. More operations • Add additional tables • Get answers using query • Modify multi-table query • Add and delete fields

  16. Common mistake • Use tables in query who are not joined. • Results in more rows than usual • For example, If we create a query on Customer table and Branch table but forget to join them. • Suppose Customers table contains 11 records, and the Branch table contains 5 records. • Since Access does not know how to interpret the unrelated tables, the results will show 55 records –every possible combination of customer and branch (11*5). • When add new table, create relationships. • Temporary join line in query will not create an actual join line between tables.

  17. Next class • Access Chapter 3 • Order of operations. • Create a calculated field. • Create expressions. • Use built-in functions. • Perform date arithmetic.

  18. Thank You Log Off

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