Database Concept and Design: SQL Queries and Commands

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30 Questions

What is the purpose of the DELETE command in SQL?

To remove tuples from a relation

What is the purpose of the SET clause in an UPDATE command?

To specify the attributes to be modified and their new values

What is the equivalent operation of the SELECT clause in RA?

Projection

What is the minimum number of clauses required in a simple SQL retrieval query?

Two

What is the purpose of the FROM clause in a SQL query?

To specify the relation to be scanned

What is the maximum number of clauses that can be present in a simple SQL retrieval query?

Four

What is the purpose of using aliases in SQL queries?

To avoid ambiguity in attribute names

What is the result of a query that selects from multiple relations without a WHERE clause?

The cross product of the relations

What is the purpose of the asterisk (*) in SQL queries?

To retrieve all attribute values

What is the result of a SELECT query without a DISTINCT keyword?

All tuples, including duplicates

What is the purpose of the WHERE clause in SQL queries?

To specify a condition for tuple selection

What is the result of a query that selects from a single relation without a WHERE clause?

All tuples from the relation

What is the primary purpose of the ALTER TABLE statement in SQL?

To modify the structure of an existing table

What is the name of the language used to define the structure of a database?

DDL (Data Definition Language)

What is the command used to remove a table from the database?

DROP TABLE

What is the purpose of the GRANT command in SQL?

To grant access to a table

What is the command used to add a new column to a table?

ALTER TABLE... ADD

What is the language used to control access to a database?

DCL (Data Control Language)

What is the purpose of the BETWEEN operator in SQL?

To check if a value is within a specified range

What is the function of the ORDER BY clause in SQL?

To sort the rows in a particular order

What is the purpose of the IN operator in SQL?

To check if a value is in a list of values

What is the purpose of transaction control commands in SQL?

To manage the execution of SQL statements

What is the result of the SQL query 'SELECT Fname, Lname FROM EMPLOYEE WHERE Super_ssn IS NULL'?

A list of employees with no supervisors

What is the feature of SQL that allows for the creation of triggers?

Object-relational systems

What is the purpose of qualifying an attribute name with the relation name in a query?

To avoid ambiguity when two tables have the same attribute name

What is the significance of the 'AS' keyword in a SQL query?

To alias a table or attribute

What is the purpose of the 'WHERE' clause in a SQL query?

To specify the conditions for which rows to include

What is the function of an alias in a SQL query?

To avoid ambiguity of attribute names in the case of queries that refer to the same relation twice

What is the result of the query: 'SELECT Fname, Lname, Address FROM EMPLOYEE as E, DEPARTMENT as D WHERE Dname='Research' AND D.Dnumber=E.Dno'?

The name and address of all employees who work for the 'Research' department

What is the purpose of the 'FROM' clause in a SQL query?

To specify the tables to be used

Test your knowledge of SQL queries, including basic retrieval, insertion, deletion, and update statements. This quiz also covers additional features of SQL, such as domain metadata and data definition language. Review the language breakdown and security commands, including CREATE, ALTER, and DROP.

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