What are the different data types in JavaScript?

Vaibhav Kothia May 30, 2023 0 Comments

The different data types in JavaScript are:

1. Number: Any numerical value, such as 42 or 3.14159.

2. String: Any set of characters within quotation marks, such as “Hello World”.

3. Boolean: A true or false value, such as true or false.

4. Array: An ordered list of values, such as [1,2,3,4,5].

5. Object: A collection of key-value pairs, such as {name: “John”, age: 30}.

6. Null: An empty value, such as null.

7. Undefined: A value that has not been defined, such as undefined.

What are the different types of MySQL databases?

Vaibhav Kothia May 30, 2023 0 Comments

1. MyISAM: MyISAM is the default storage engine in MySQL. It is a non-transactional storage engine that supports table-level locking. Example: MyISAM is used for data warehousing and web applications.

2. InnoDB: InnoDB is a transactional storage engine that supports row-level locking. It is the most popular storage engine for transactional applications. Example: InnoDB is used for online transaction processing (OLTP) applications.

3. Memory: Memory is a storage engine that stores data in memory. It is a non-transactional storage engine that supports table-level locking. Example: Memory is used for temporary tables and for high-performance applications.

4. Archive: Archive is a storage engine that stores data in a compressed format. It is a non-transactional storage engine that supports table-level locking. Example: Archive is used for storing historical data.

5. CSV: CSV is a storage engine that stores data in comma-separated values (CSV) format. It is a non-transactional storage engine that supports table-level locking. Example: CSV is used for importing and exporting data.

What is the difference between null and undefined?

Vaibhav Kothia May 26, 2023 0 Comments

Null is a value that indicates the absence of a value. It is often used to indicate an intentional lack of a value, while undefined is a value that indicates that a variable has not been assigned a value.

Example:

Null:
let x = null;

Undefined:
let y;

What are the different types of data types supported by PostgreSQL?

Vaibhav Kothia May 26, 2023 0 Comments

PostgreSQL supports a variety of data types:

1. Numeric Types:
– Integer (e.g. 1,2,3)
– Real (e.g. 3.1415)
– Double Precision (e.g. 2.718281828459045)
– Numeric (e.g. 12345.6789)
– Decimal (e.g. 123.45)

2. Character Types:
– Character (e.g. ‘A’)
– Character Varying (e.g. ‘Hello World’)
– Text (e.g. ‘This is a text’)

3. Date/Time Types:
– Date (e.g. ‘2021-02-19’)
– Time (e.g. ‘15:30:00’)
– Timestamp (e.g. ‘2021-02-19 15:30:00’)
– Interval (e.g. ‘1 day’)

4. Boolean Type:
– Boolean (e.g. true or false)

5. Geometric Types:
– Point (e.g. (1.5, 2.5))
– Line (e.g. [ (1.5, 2.5), (2.5, 3.5) ])
– Box (e.g. ( (1.5, 2.5), (2.5, 3.5) ))
– Circle (e.g. )

6. Network Address Types:
– Inet (e.g. ‘127.0.0.1/32’)
– Cidr (e.g. ‘127.0.0.1/24’)

7. Bit String Types:
– Bit (e.g. B’1010’)
– Bit Varying (e.g. B’1001’)

8. UUID Types:
– UUID (e.g. ‘a0eebc99-9c0b-4ef8-bb6d-6bb9bd380a11’)