What is the purpose of the "INNER JOIN" keyword?

To return records that have matching values in both tables

To merge only the primary keys of two unrelated tables

To combine all rows from all tables regardless of matches

To create a copy of a table within the same database schema

What is a "Primary Key"?

A column that uniquely identifies each row in a table

The first column created during the table definition

The encrypted password used to access the database server

A metadata tag that describes the purpose of the database

What is a "Foreign Key"?

A column that establishes a relationship between two tables

A secondary index used to speed up complex query joins

A backup identifier used when the primary key is corrupted

An external API key used to connect to third-party databases

What is the "LEFT JOIN" keyword used for?

To return all records from the left table and matched records from the right

To return only the records that exist in the left table but not the right

To merge columns from two tables without checking for matching values

To remove the right-most columns from the final query result

What is "Database Normalization"?

Organizing data to minimize redundancy and maximize data integrity

The process of compressing data to save physical disk space

Converting all non-standard data types into string formats

The automated process of fixing corrupted database indexes

What is the "GROUP BY" clause used for?

To arrange rows with identical values into summary rows

To arrange the query results in alphabetical order

To limit the number of users who can access a table

To join multiple tables into a single virtual view

What is the "HAVING" clause used for?

To filter groups based on a condition after aggregation

To filter rows before they are processed by a join

To define a primary key on a newly created table

To check if a subquery returns any valid results

What does "NULL" represent in SQL?

The state of a value being missing or unknown

A value of zero for numerical columns

An empty string within a character column

A boolean value indicating a false condition

What is the purpose of the "LIKE" operator?

To search for a specified pattern within a string column

To verify that two tables have identical column names

To join tables that have similar data structures

To sort data based on the similarity of text values

What is a "Transaction" in SQL?

A unit of work that succeeds or fails as a complete set

A single data transfer between two different servers

The history of all changes made to a specific record

An individual row within a financial ledger table

What is an "Index" used for?

To provide a faster lookup path for retrieving data rows

To define the order in which columns appear in a query

To map the physical location of the database on the disk

To count the total number of tables in a database schema

What is a "View" in SQL?

A virtual table based on the results of a stored query

A graphical user interface for browsing database tables

A snapshot of the database used for backup and recovery

A read-only permission level assigned to guest users

What does the "AS" keyword do?

It creates a temporary alias for a column or table in a query

It permanentely renames a column in the database schema

It assigns a specific data type to a new table column

It encrypts the results of a SELECT statement

What is a "Constraint" in SQL?

A rule enforced on columns to ensure data accuracy and reliability

A physical limitation on the size of the database file

A performance bottleneck caused by too many concurrent users

A piece of code that prevents a table from being deleted

What is "Referential Integrity"?

The consistency between tables maintained via foreign key constraints

The guarantee that every query will return at least one row

The encryption level applied to data while it is in transit

The speed at which a primary key can be looked up in a query

What does the "UNION" operator do?

It combines the results of two SELECT statements into one set

It multiplies the numeric values of two distinct result sets

It joins two tables based on a common identifier

It creates a link between a primary and secondary database

What is a "Stored Procedure"?

A group of SQL statements that can be saved and reused

A hardware configuration used to store large database files

A log of all actions taken by a database administrator

An automated backup routine scheduled by the system

What is the "TRUNCATE" command?

It removes all records from a table while keeping the structure

It deletes the table structure and its associated permissions

It limits the number of characters allowed in a string column

It hides specific rows from users without deleting them

What does "ACID" stand for in database terms?

Atomicity, Consistency, Isolation, Durability

Automated, Clean, Integrated, Distributed

Access, Control, Integrity, Data

Allocate, Commit, Initialize, Deploy

What is the difference between "DELETE" and "TRUNCATE"?

DELETE can remove specific rows, whereas TRUNCATE empties the whole table

DELETE is used for NoSQL databases, while TRUNCATE is for SQL only

TRUNCATE can be rolled back in all databases, but DELETE cannot

DELETE removes the table structure, but TRUNCATE keeps it

Quizzes

SQL Databases Quizzes

SQL: Query Fundamentals & Database Concepts

Mohammad Abu Mattar20 QuestionsBeginnerPublished: 21 Feb, 2026

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SQL: Query Fundamentals & Database Concepts

Up to 20 questions, shuffled on every run

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Welcome to the SQL Basics Quiz! Relational databases are the bedrock of modern applications. Whether you’re a developer writing queries or a DevOps engineer maintaining a production cluster, mastering SQL is essential for data integrity and system performance. This quiz will test your knowledge from basic selection to complex joins and database management. Good luck!

Answer key and explanations20 questions

The quiz above draws 20 questions at random from these 30, so a second attempt will not be the same run. Everything in the pool is listed here.

What does "SQL" stand for?
AnswerStructured Query Language
Which SQL statement is used to extract data from a database?
AnswerSELECT
Which clause is used to filter records based on a specific condition?
AnswerWHERE
What is the purpose of the "INNER JOIN" keyword?
AnswerTo return records that have matching values in both tables
Which SQL command is used to update existing data in a table?
AnswerUPDATE
What is a "Primary Key"?
AnswerA column that uniquely identifies each row in a table
What is a "Foreign Key"?
AnswerA column that establishes a relationship between two tables
How do you sort the result set in SQL?
AnswerORDER BY
What is the "LEFT JOIN" keyword used for?
AnswerTo return all records from the left table and matched records from the right
What is "Database Normalization"?
AnswerOrganizing data to minimize redundancy and maximize data integrity
Which SQL command is used to remove a table from a database?
AnswerDROP
What is the "GROUP BY" clause used for?
AnswerTo arrange rows with identical values into summary rows
Which aggregate function finds the number of rows in a table?
AnswerCOUNT()
What is the "HAVING" clause used for?
AnswerTo filter groups based on a condition after aggregation
What does "NULL" represent in SQL?
AnswerThe state of a value being missing or unknown
Which keyword is used to return only unique values?
AnswerDISTINCT
What is the purpose of the "LIKE" operator?
AnswerTo search for a specified pattern within a string column
What is a "Transaction" in SQL?
AnswerA unit of work that succeeds or fails as a complete set
What is an "Index" used for?
AnswerTo provide a faster lookup path for retrieving data rows
Which SQL command is used to add new rows to a table?
AnswerINSERT INTO
What is a "View" in SQL?
AnswerA virtual table based on the results of a stored query
What does the "AS" keyword do?
AnswerIt creates a temporary alias for a column or table in a query
What is a "Constraint" in SQL?
AnswerA rule enforced on columns to ensure data accuracy and reliability
Which command changes the structure of an existing table?
AnswerALTER TABLE
What is "Referential Integrity"?
AnswerThe consistency between tables maintained via foreign key constraints
What does the "UNION" operator do?
AnswerIt combines the results of two SELECT statements into one set
What is a "Stored Procedure"?
AnswerA group of SQL statements that can be saved and reused
What is the "TRUNCATE" command?
AnswerIt removes all records from a table while keeping the structure
What does "ACID" stand for in database terms?
AnswerAtomicity, Consistency, Isolation, Durability
What is the difference between "DELETE" and "TRUNCATE"?
AnswerDELETE can remove specific rows, whereas TRUNCATE empties the whole table

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