SQL - Common Jobs

Welcome to your SQL

SQL

Which SQL keyword is used to remove duplicate rows from a result set?

UNIQUE

DISTINCT

REMOVE

DIFFERENT

SQL

Which SQL clause is used to filter records?

WHERE

ORDER BY

GROUP BY

HAVING

SQL

Which SQL command is used to save all changes made during the transaction?

COMMIT

EXECUTE

APPLY

SAVE

SQL

What is the purpose of the EXPLAIN command in SQL?

Explains syntax errors

Shows data

Displays the execution plan of a query

Lists all tables

SQL

What does a clustered index do?

Creates a secondary data structure

Sorts and stores data rows in order

Optimizes joins

Prevents duplication

SQL

Which of these joins returns all records when there is a match in either table?

INNER JOIN

LEFT JOIN

FULL OUTER JOIN

RIGHT JOIN

SQL

What will the query SELECT COUNT(DISTINCT department_id) return?

Total unique department IDs

Total null department IDs

Total employees

Total departments

SQL

Which of the following is used to prevent duplicate entries in a table?

CHECK constraint

DEFAULT constraint

UNIQUE constraint

FOREIGN KEY constraint

SQL

What does the ON DELETE CASCADE option do?

Prevents deletion

Deletes related rows when a parent row is deleted

Ignores delete operation

Deletes all records in the table

SQL

Which of the following can improve query performance?

Using SELECT *

Adding indexes

Removing indexes

Increasing columns

SQL

What is a subquery?

A stored procedure

A query that runs independently

A system query

A query inside another query

SQL

Which function is used to return the current date in SQL?

DATE()

SYSDATE()

NOW()

CURRENT()

SQL

Which SQL statement is used to combine rows from two or more tables?

INTERSECT

COMBINE

JOIN

UNION

SQL

What does the GROUP BY clause do?

Filters data

Groups rows with the same values

Sorts data

Deletes duplicates

SQL

Which SQL constraint ensures that all values in a column are unique?

FOREIGN KEY

UNIQUE

NOT NULL

PRIMARY KEY

SQL

Which SQL statement is used to create a new table?

MAKE TABLE

NEW TABLE

ADD TABLE

CREATE TABLE

SQL

Which function returns the average value of a numeric column?

MEDIAN()

MEAN()

SUM()

AVG()

What is a foreign key used for?

To allow duplicate records

To encrypt data

To uniquely identify each record

To enforce referential integrity between tables

SQL

What is the difference between INNER JOIN and LEFT JOIN?

LEFT JOIN excludes matching rows

Both are the same

INNER JOIN includes unmatched rows

LEFT JOIN includes all rows from the left table

SQL

Which keyword is used to rename a column or table in SQL?

ALIAS

RENAME

UPDATE

SQL

Which of the following is a valid SQL data type?

Integer

Float

String

Both a and c

SQL

What is the purpose of the LIMIT clause?

To filter rows

To count rows

To specify the maximum number of rows to return

To define constraints

SQL

Which aggregate function returns the highest value in a column?

UPPER()

MAX()

HIGH()

TOP()

SQL

Which SQL keyword is used to sort results?

FILTER

GROUP BY

ORDER BY

SORT

SQL

Which of the following statements will delete all rows in a table named ‘students’? a) b) c) d)

CLEAR TABLE students;

DELETE FROM students;

DROP students;

REMOVE * FROM students;