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31 Cards in this Set
- Front
- Back
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Whats a view?
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an individuals picture of the database
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benefits of a view?
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security,simplification,less involved than full database, each user has his own view, data independence
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Whats a defining query?
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Select statement that creates the view. The query does not create a table.
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Does the DBMS run the query in this form?
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No, the query that is actually executed is the merger of this query and the create view query.
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Whats an index?
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similar to a book index. they speed up data retrieval. record numbers automatically assigned by DBMS
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Whats an index key?
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a field on which the index is built
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Disadvantage of indexing
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occupy disk space, dbms must update index when data is updated
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What is db security?
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prevention of unauthorized access to db
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What statement provides privileges to users?
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GRANT
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what statement remove privileges?
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REVOKE
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2 kinds of integrity rules must be followed. What are they?
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entity integrity, referential integrity
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What is entity integrity?
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Primary keys cant accept null values
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What is referential integrity?
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value of Foreign key fields that correspond to table B must match the value of the primary key for the same row in table B or be null
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2 kinds of integrity rules must be followed. What are they?
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entity integrity, referential integrity
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what is legal-values integrity?
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Can only enter certain values for a field. (implemented with CHECK statement)
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What is entity integrity?
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Primary keys cant accept null values
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What are some examples of structure changes in a DB?
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deleting tables, changing field characteristics, deleting/adding fields, adding,deleting indexes.
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What is referential integrity?
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value of Foreign key fields that correspond to table B must match the value of the primary key for the same row in table B or be null
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What statement is used to change DB structure?
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ALTER TABLE
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what is legal-values integrity?
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Can only enter certain values for a field. (implemented with CHECK statement)
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Whats a system catalog?
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contains data about the database (metadata) maintained automatically by database
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What are some examples of structure changes in a DB?
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deleting tables, changing field characteristics, deleting/adding fields, adding,deleting indexes.
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Whats a stored procedure?
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query that resides on the server andand is run often.
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What statement is used to change DB structure?
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ALTER TABLE
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Benefits of stored procedure?
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convenience and performance
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Whats a system catalog?
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contains data about the database (metadata) maintained automatically by database
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Whats a delimiter?
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semicolon at the end of a MySQL command
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Whats a stored procedure?
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query that resides on the server andand is run often.
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Benefits of stored procedure?
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convenience and performance
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Whats a delimiter?
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semicolon at the end of a MySQL command
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What is a trigger?
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action that occurs automatically after an operation (such as INSERT, UPDATE, DELETE)
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