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Computer Science & Engineering 2111. CSE 2111 Lecture Querying a Database. What is a Database Query?. A request for information from a database To extract information from the Database you must use a Query which is a “question” or “request” Criterion
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Computer Science & Engineering 2111 CSE 2111 Lecture Querying a Database CSE 2111 Lecture- Querying a Database
What is a Database Query? • A request for information from a database • To extract information from the Database you must use a Query which is a “question” or “request” • Criterion • An expression that tells the DBMS which records to retrieve • Make up of conditions • Can be one conditions or many • When you run the query a dynaset, or subset of the database is displayed. • You can make changes to this dynaset and the changes will be reflected in your database, because the dynaset is just a view of your database. CSE 2111 Lecture- Querying a Database
Query By Example (QBE) Grid Dynaset created when Query is run CSE 2111 Lecture- Querying a Database
Structured Query Language (SQL) • SQL is the language you use to talk to the database • MS Access 2010 supplies a graphical user interface (GUI) called the Query By Example Grid or (QBE) grid • MS Access 2010 creates the SQL for you. CSE 2111 Lecture- Querying a Database
SQL Created from QBE Grid CSE 2111 Lecture- Querying a Database