SQL INTERVIEW QUESTION CHEATSHEET
SQL(stands for Structured Query Language)is the popular query language to manage databases. So, here is a collection of the most asked SQL interview questions to help you prepare
Please Like & Retweet
🧵A Thread 🧵
#100DaysOfCode
#SQL #Coding
SQL(stands for Structured Query Language)is the popular query language to manage databases. So, here is a collection of the most asked SQL interview questions to help you prepare
Please Like & Retweet
🧵A Thread 🧵
#100DaysOfCode
#SQL #Coding
What is Database?
A database is an organized collection of data, stored and retrieved digitally from a remote or local computer system. Databases can be vast and complex, and such databases are developed using fixed design and modeling approaches.
#100DaysOfCode #SQL #Coding
A database is an organized collection of data, stored and retrieved digitally from a remote or local computer system. Databases can be vast and complex, and such databases are developed using fixed design and modeling approaches.
#100DaysOfCode #SQL #Coding
What is DBMS?
DBMS stands for Database Management System. DBMS is a system software responsible for the creation, retrieval, updating, and management of the database.
#100DaysOfCode #SQL #Coding
DBMS stands for Database Management System. DBMS is a system software responsible for the creation, retrieval, updating, and management of the database.
#100DaysOfCode #SQL #Coding
What is SQL?
SQL stands for Structured Query Language. It is the standard language for relational database management systems. It is especially useful in handling organized data comprised of entities and relations between different entities of the data.
#100DaysOfCode #SQL #IT
SQL stands for Structured Query Language. It is the standard language for relational database management systems. It is especially useful in handling organized data comprised of entities and relations between different entities of the data.
#100DaysOfCode #SQL #IT
What is the difference between SQL and MySQL?
SQL is a standard language for retrieving and manipulating structured databases. On the contrary, MySQL is a relational database management system, like SQL Server, Oracle, that is used to manage SQL databases.
#100DaysOfCode #SQL
SQL is a standard language for retrieving and manipulating structured databases. On the contrary, MySQL is a relational database management system, like SQL Server, Oracle, that is used to manage SQL databases.
#100DaysOfCode #SQL
What are Tables and Fields?
A table is an organized collection of data stored in the form of rows and columns. Columns can be categorized as vertical and rows as horizontal. The columns in a table are called fields while the rows can be referred to as records
#100DaysOfCode
A table is an organized collection of data stored in the form of rows and columns. Columns can be categorized as vertical and rows as horizontal. The columns in a table are called fields while the rows can be referred to as records
#100DaysOfCode
What is a Primary Key?
The PRIMARY KEY constraint uniquely identifies each row in a table. It must contain UNIQUE values and has an implicit NOT NULL constraint.
A table in SQL is strictly restricted to have one and only one primary key.
#100DaysOfCode
The PRIMARY KEY constraint uniquely identifies each row in a table. It must contain UNIQUE values and has an implicit NOT NULL constraint.
A table in SQL is strictly restricted to have one and only one primary key.
#100DaysOfCode
What is a UNIQUE constraint?
A UNIQUE constraint ensures all values in a column are different. This provides uniqueness for the column(s) and helps identify each row uniquely. Unlike the primary key, there can be multiple unique constraints defined per table.
#100DaysOfCode
A UNIQUE constraint ensures all values in a column are different. This provides uniqueness for the column(s) and helps identify each row uniquely. Unlike the primary key, there can be multiple unique constraints defined per table.
#100DaysOfCode
What is a Foreign Key?
A FOREIGN KEY comprises of single or collection of fields in a table that essentially refers to the PRIMARY KEY in another table. Foreign key constraint ensures referential integrity in the relation between two tables.
#100DaysOfCode #SQL #Coding
A FOREIGN KEY comprises of single or collection of fields in a table that essentially refers to the PRIMARY KEY in another table. Foreign key constraint ensures referential integrity in the relation between two tables.
#100DaysOfCode #SQL #Coding
What is a Join? List its different types.
The SQL Join clause is used to combine records (rows) from two or more tables in a SQL database based on a related column between the two.
Types -
INNER JOIN
LEFT OUTER JOIN
RIGHT OUTER JOIN
FULL OUTER JOIN
#100DaysOfCode
The SQL Join clause is used to combine records (rows) from two or more tables in a SQL database based on a related column between the two.
Types -
INNER JOIN
LEFT OUTER JOIN
RIGHT OUTER JOIN
FULL OUTER JOIN
#100DaysOfCode
What is a Query?
A query is a request for data or information from a database table or combination of tables. A database query can be either a select query or an action query.
#100DaysOfCode
A query is a request for data or information from a database table or combination of tables. A database query can be either a select query or an action query.
#100DaysOfCode
SQL create and drop database?
Create database db_name -
=> CREATE DATABASE db_name;
Drop database db_name -
=> DROP DATABASE db_name;
#100DaysOfCode #SQL #Database #Coding
Create database db_name -
=> CREATE DATABASE db_name;
Drop database db_name -
=> DROP DATABASE db_name;
#100DaysOfCode #SQL #Database #Coding
Create and drop a table in SQL?
CREATE TABLE table_name (
column1 datatype,
column2 datatype,
column3 datatype,
....
);
DROP TABLE table_name;
#100DaysOfCode #SQL #Database #Query #codingisfun
CREATE TABLE table_name (
column1 datatype,
column2 datatype,
column3 datatype,
....
);
DROP TABLE table_name;
#100DaysOfCode #SQL #Database #Query #codingisfun
What is the difference between DROP and TRUNCATE statements?
If a table is dropped, all things associated with the tables are dropped as well. However, if a table is truncated, none of the above problems exist and the table retains its original structure.
#100DaysOfCode #SQL
If a table is dropped, all things associated with the tables are dropped as well. However, if a table is truncated, none of the above problems exist and the table retains its original structure.
#100DaysOfCode #SQL
How do we use the DISTINCT statement?
The DISTINCT statement is used with the SELECT statement. If a record contains duplicate values then DISTINCT will select different values among duplicate records.
Syntax-
SELECT DISTINCT column_name
FROM table_name;
#100DaysOfCode #SQL
The DISTINCT statement is used with the SELECT statement. If a record contains duplicate values then DISTINCT will select different values among duplicate records.
Syntax-
SELECT DISTINCT column_name
FROM table_name;
#100DaysOfCode #SQL
What is ACID property?
In order to maintain consistency in a database, before and after the transaction, certain properties are followed. These are called ACID properties.
- Atomicity
- Consistency
- Isolation
- Durability
#100DaysOfCode #Database #SQL #Query #codingisfun
In order to maintain consistency in a database, before and after the transaction, certain properties are followed. These are called ACID properties.
- Atomicity
- Consistency
- Isolation
- Durability
#100DaysOfCode #Database #SQL #Query #codingisfun
How many Aggregate functions are available in SQL?
SQL Aggregate functions calculate values from multiple columns and return a single value. There are 7 aggregate functions in SQL:
1. AVG()
2. COUNT()
3. MAX()
4. MIN()
5. SUM()
6. FIRST()
7. LAST()
#100DaysOfCode #SQL #Query
SQL Aggregate functions calculate values from multiple columns and return a single value. There are 7 aggregate functions in SQL:
1. AVG()
2. COUNT()
3. MAX()
4. MIN()
5. SUM()
6. FIRST()
7. LAST()
#100DaysOfCode #SQL #Query
What is View in SQL?
A View can be defined as a virtual table that contains rows and columns with fields from one or more tables.
Syntax:
CREATE VIEW view_name AS
SELECT column_name(s)
FROM table_name
WHERE condition
#100DaysOfCode #SQL #Database #Query #codingisfun
A View can be defined as a virtual table that contains rows and columns with fields from one or more tables.
Syntax:
CREATE VIEW view_name AS
SELECT column_name(s)
FROM table_name
WHERE condition
#100DaysOfCode #SQL #Database #Query #codingisfun
What is SQL Injection?
SQL Injection is a type of database attack technique where malicious SQL statements are inserted into an entry field of the database in a way that once it is executed, the database is exposed to an attacker for the attack.
#100DaysOfCode #codingisfun
SQL Injection is a type of database attack technique where malicious SQL statements are inserted into an entry field of the database in a way that once it is executed, the database is exposed to an attacker for the attack.
#100DaysOfCode #codingisfun
What is Normalization? How many Normalization forms are there?
Normalization is used to organize the data tor remove redundancies.
5 type of normal form:
First Normal Form(1NF)
First Normal Form(2NF)
Third Normal Form(3NF)
Fourth Normal Form(BCNF)
#100DaysOfCode #codingisfun
Normalization is used to organize the data tor remove redundancies.
5 type of normal form:
First Normal Form(1NF)
First Normal Form(2NF)
Third Normal Form(3NF)
Fourth Normal Form(BCNF)
#100DaysOfCode #codingisfun
What is a Relationship? How many types of Relationships are there?
The relationship can be defined as the connection between more than one table in the database.
Type of Relationship -
1. One to One
2. Many to One
3. Many to Many
4. One to Many
#100DaysOfCode #codingisfun #SQL
The relationship can be defined as the connection between more than one table in the database.
Type of Relationship -
1. One to One
2. Many to One
3. Many to Many
4. One to Many
#100DaysOfCode #codingisfun #SQL
How to select all records from the table?
To select all the records from the table we need to use the following syntax:
SELECT * FROM table_name;
#100DaysOfCode #SQL #codingisfun #Database #100DaysOfMLCode #querytip
To select all the records from the table we need to use the following syntax:
SELECT * FROM table_name;
#100DaysOfCode #SQL #codingisfun #Database #100DaysOfMLCode #querytip
Difference between TRUNCATE, DELETE, and DROP commands?
DELETE removes some or all rows from a table based on the condition.
TRUNCATE removes ALL rows from a table by deallocating the memory pages.
DROP command removes a table from the database completely.
#100DaysOfCode #SQL
DELETE removes some or all rows from a table based on the condition.
TRUNCATE removes ALL rows from a table by deallocating the memory pages.
DROP command removes a table from the database completely.
#100DaysOfCode #SQL
Difference between TRUNCATE, DELETE, and DROP commands?
DELETE removes some or all rows from a table based on the condition.
TRUNCATE removes ALL rows from a table by deallocating the memory pages.
DROP command removes a table from the database completely.
#100DaysOfCode #SQL
DELETE removes some or all rows from a table based on the condition.
TRUNCATE removes ALL rows from a table by deallocating the memory pages.
DROP command removes a table from the database completely.
#100DaysOfCode #SQL
• • •
Missing some Tweet in this thread? You can try to
force a refresh
