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Questions and Answers
Which SQL command is used to revoke privileges from a user?
Which SQL command is used to revoke privileges from a user?
What is the correct syntax to create a table named Student with columns ID, Name, and Age?
What is the correct syntax to create a table named Student with columns ID, Name, and Age?
Which SQL query would you use to display the flight numbers of all flights that arrive at LaGuardia Airport later today?
Which SQL query would you use to display the flight numbers of all flights that arrive at LaGuardia Airport later today?
What type of index is used to improve the performance of queries that return large result sets?
What type of index is used to improve the performance of queries that return large result sets?
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What is the purpose of the REVOKE command?
What is the purpose of the REVOKE command?
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Which of the following is a characteristic of a clustered index?
Which of the following is a characteristic of a clustered index?
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What is the purpose of the CREATE TABLE command?
What is the purpose of the CREATE TABLE command?
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Which of the following is not a data type in SQL?
Which of the following is not a data type in SQL?
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What type of index would improve the efficiency of a query that searches for a specific category of products?
What type of index would improve the efficiency of a query that searches for a specific category of products?
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Which SQL keyword is used to search for a specific pattern in a string?
Which SQL keyword is used to search for a specific pattern in a string?
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What is the likely cause of a stored procedure returning all null values?
What is the likely cause of a stored procedure returning all null values?
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What is the purpose of a primary key in a database table?
What is the purpose of a primary key in a database table?
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What is the benefit of creating an index on a frequently queried column?
What is the benefit of creating an index on a frequently queried column?
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What is the primary advantage of using a stored procedure in a database?
What is the primary advantage of using a stored procedure in a database?
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What is the purpose of the WHERE clause in the NorthAmericanMammals_View?
What is the purpose of the WHERE clause in the NorthAmericanMammals_View?
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What happens to the result set of a view when the underlying table data is modified?
What happens to the result set of a view when the underlying table data is modified?
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What is the purpose of the INTERSECT keyword in SQL?
What is the purpose of the INTERSECT keyword in SQL?
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What is a benefit of using stored procedures?
What is a benefit of using stored procedures?
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What is the purpose of normalizing a database?
What is the purpose of normalizing a database?
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What type of join is used to retrieve all customers and their orders, as well as customers who have no orders?
What type of join is used to retrieve all customers and their orders, as well as customers who have no orders?
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What is the purpose of the AS keyword in a CREATE VIEW statement?
What is the purpose of the AS keyword in a CREATE VIEW statement?
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What is the purpose of the UPDATE VIEW statement?
What is the purpose of the UPDATE VIEW statement?
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Study Notes
SQL Syntax
- To remove a user from a database object, use the
REVOKE
orREMOVE
command, followed by the user name and the object name (e.g.REVOKE User1 FROM Customer
orC.REMOVE User1 FROM Customer
). - To create a database object, use the
CREATE
command followed by the object type (e.g.TABLE
), the object name, and the column definitions (e.g.CREATE TABLE Student (ID INT, Name VARCHAR(100), Age INT)
).
Querying
- To filter data based on a specific condition, use the
WHERE
clause (e.g.SELECT FlightNumber FROM Flight WHERE DestinationAirport = ‘LGA’ AND ArrivalTime > GETDATE()
). - To sort data in descending order, use the
ORDER BY
clause with theDESC
keyword (e.g.ORDER BY ArrivalTime DESC
).
Indexing
- A clustered index improves the performance of queries that retrieve large result sets.
- A clustered index does not improve the performance of queries that access columns randomly.
- A primary key or unique constraint can be used in conjunction with a clustered index.
Query Optimization
- To optimize a query that searches for data based on a specific category, create a non-clustered index on the category column (e.g.
CREATE INDEX ON Product (Category)
). - A clustered index on the
ProductName
column would not improve the performance of this query. - A non-clustered index on the
Price
column would not improve the performance of this query.
Query Keywords
- To search for data that contains a specific character or pattern, use the
LIKE
keyword in theWHERE
clause (e.g.SELECT * FROM Product WHERE ProductName LIKE '%Science%'
). - The
BETWEEN
keyword is used to filter data within a specific range. - The
IN
keyword is used to filter data based on a list of values.
Stored Procedures
- A stored procedure can return null values if the columns used in the query contain null values.
- The
+
operator can be used to concatenate character data. - The
JOIN
keyword is not required in theSELECT
statement.
Views
- A view is a virtual table based on the result of a query.
- If the underlying data is deleted, the view will return an empty result set.
- A view can be created using the
CREATE VIEW
command, followed by the view name and the query definition (e.g.CREATE VIEW [dbo].[NorthAmericanMammals_View] AS SELECT a.Id, a.Name FROM Animal a WHERE a.Class = ‘Mammals’ AND a.InNorthAmerica = 1
).
Normalization
- To normalize a database to first normal form, exclude repeating groups and avoid duplicate rows.
- Composite keys and foreign keys are not excluded in first normal form.
Joins
- A full join returns all rows from both tables, including those that do not have matching values.
- An inner join returns only the rows that have matching values in both tables.
- A full join is used to retrieve all customers and their orders, including customers who have no orders.
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Description
Learn how to create views in SQL that filter specific data from tables, such as selecting products from a certain category or mammals from a specific region.