SQL Queries for Filtering States
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SQL Queries for Filtering States

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Questions and Answers

What is the purpose of the query in option A?

  • To retrieve a specific employee's name (correct)
  • To delete an employee from the database
  • To insert a new employee into the database
  • To update an existing employee's information
  • What is the purpose of the query in option C?

  • To delete an employee from the database
  • To insert a new employee into the database (correct)
  • To retrieve an employee's name
  • To update an existing employee's information
  • What is the purpose of the query in option D?

  • To add a new column to the Employee table (correct)
  • To modify an existing column in the Employee table
  • To rename a column in the Employee table
  • To remove a column from the Employee table
  • Which query will retrieve ItemName and Price when 'chocolate' appears in the ItemDescription column?

    <p>SELECT ItemName, Price FROM Products WHERE ItemDescription LIKE '%chocolate%';</p> Signup and view all the answers

    What is the purpose of creating a composite key?

    <p>To improve data consistency across multiple tables</p> Signup and view all the answers

    What type of database constraint ensures that a column does not contain null values?

    <p>NOT NULL</p> Signup and view all the answers

    What is the purpose of a primary key in a database table?

    <p>To uniquely identify a single record in a table</p> Signup and view all the answers

    What is the purpose of a foreign key in a database table?

    <p>To establish a relationship between multiple tables</p> Signup and view all the answers

    What is the correct SQL query to select all orders from the Orders table where the ship state is not 'TX' or 'AZ'?

    <p>SELECT * FROM Orders WHERE NOT ship_state = 'TX' OR NOT ship_state = 'AZ'</p> Signup and view all the answers

    What is the correct syntax to remove a column from a table in SQL?

    <p>ALTER TABLE Customers DROP COLUMN SSN;</p> Signup and view all the answers

    What is the correct order of clauses in a SQL query to determine whether a value appears only once in a table?

    <p>SELECT, FROM, WHERE, GROUP BY, HAVING</p> Signup and view all the answers

    What is the correct statement to remove a view from a database?

    <p>DROP VIEW EmployeeView</p> Signup and view all the answers

    What should you apply to the Employee table to ensure that an employee can be assigned to only an existing department?

    <p>A foreign key</p> Signup and view all the answers

    What is the correct statement to remove a foreign key from a table?

    <p>ALTER TABLE</p> Signup and view all the answers

    What is the purpose of a foreign key in a relational database?

    <p>To establish a relationship between two tables</p> Signup and view all the answers

    What is the correct syntax to alter a table to add a new column in SQL?

    <p>ALTER TABLE Customers ADD COLUMN SSN;</p> Signup and view all the answers

    What is a primary key constraint in a relational database?

    <p>A constraint that ensures each row in a table is unique</p> Signup and view all the answers

    What is the correct syntax to create a composite primary key in SQL?

    <p>CREATE TABLE Order (OrderID INTEGER, OrderItemID INTEGER, PRIMARY KEY (OrderID, OrderItemID))</p> Signup and view all the answers

    Which data type is suitable for storing financial data in a database table?

    <p>Decimal</p> Signup and view all the answers

    What is the purpose of the UPDATE statement in SQL?

    <p>To update existing records in a table</p> Signup and view all the answers

    How do you specify a condition in an UPDATE statement to update only specific records?

    <p>Using the WHERE clause</p> Signup and view all the answers

    What is the purpose of the PRIMARY KEY constraint in a relational database?

    <p>To ensure data integrity by preventing duplicate values</p> Signup and view all the answers

    Which SQL statement is used to count the number of rows in a table?

    <p>SELECT COUNT(*)</p> Signup and view all the answers

    What is the purpose of the UNIQUE constraint in a relational database?

    <p>To ensure each value in a column is unique</p> Signup and view all the answers

    Study Notes

    SQL Queries

    • SELECT statement can be used to retrieve data from a table, with NOT operator to exclude certain values, e.g., SELECT * FROM Orders WHERE NOT ship_state = 'TX' AND NOT ship_state = 'AZ'.
    • Using OR instead of AND in the query can alter the result, including more records, e.g., SELECT * FROM Orders WHERE NOT ship_state = 'TX' OR NOT ship_state = 'AZ'.

    Database Modifications

    • To remove a column from a table, use ALTER TABLE Customers DROP COLUMN SSN;.
    • To drop a view, use DROP VIEW EmployeeView;.
    • To remove a foreign key, use ALTER TABLE ... DROP FOREIGN KEY ...;.

    Query Errors

    • A query with a syntax error may be due to incorrect ordering of clauses, e.g., SELECT Title FROM Movie WHERE Title = 'Sample Movie' ORDER BY Title GROUP BY Title HAVING COUNT(*) = 1.
    • Correcting the query by removing the ORDER BY clause can resolve the error.

    Table Structure

    • Each row in a table must be unique.
    • Each column name in a table must be unique.
    • A value in a field in a table does not have to be unique.

    Data Types

    • For financial calculations, a decimal data type is recommended, e.g., for storing charge amounts.

    Updating Tables

    • To update a table, use UPDATE LoanedBooks SET Books = 0 WHERE (NAME = 'Harry' AND City = 'San Francisco');.
    • Use specific conditions to update the correct record.

    Retrieving Data

    • To return the number of rows in a table, use SELECT COUNT(*) FROM Employee;.
    • To retrieve specific data, use SELECT ItemName, Price FROM Products WHERE ItemDescription LIKE '%chocolate%';.

    Composite Key

    • A composite key is created when a primary key consists of multiple columns, e.g., CREATE TABLE Order (OrderID INTEGER, OrderItemID INTEGER, PRIMARY KEY (OrderID, OrderItemID));.

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    Related Documents

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    Description

    This quiz tests your understanding of SQL queries, specifically in filtering data based on state information. Identify the correct SQL query to retrieve data excluding certain states.

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