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Scalar function Scalar function:  Scalar function takes one or more parameters and returns a single value These functions are based on user input, these too returns single value.  UCASE() LCASE()  MID()  LEN()  ROUND()  NOW()  FORMAT()

Aggregate Functions Aggregate Functions : An aggregate function performs a calculation on a set of values, and returns a single value. Except for COUNT, aggregate functions ignore null values. Aggregate functions are often used with the GROUP BY clause of the SELECT statement. aggregate functions return the same value each time that they are called, when called with a specific set of input values. The following are the commonly used SQL aggregate functions: AVG() – returns the average of a set. COUNT() – returns the number of items in a set. MAX() – returns the maximum value in a set. MIN() – returns the minimum value in a set. SUM() – returns the sum of all or distinct values in a set.

what is a public key encryption?? In public key encryption we have two keys: - one is public and another is private.We use these keys for secure communicating with each outher.Public key is used by sender to encrypt his message and private key is used by receiver to decript this message. Example :- Suppose I want to get message from many resources so  I will distribute public key to all the user who want to send me message and I keep private key to decrypt the message which user send to me.

what is PGP (Pretty Good Privacy) ??  Father of PGP :- Phil Zimmerman PGP is a encryption program that provides cryptographic privacy and authentication for data communication.It is the most popular standard for email encryption.

what is a RSA encryption ?? RSA : - Rivest-Shamir-Adleman (these are the name of RSA inventors.) RSA is a encryption algorithm which is used to send message securely in the internet.RSA is a public key algorithm widely used for secure data transmission.In public key algorithm we used two keys for data transmission : one is public and another is private key.We use public key for data encryption and private key for data decryption .  RSA is based on the principle that it is easy to multiply large numbers, but factoring large numbers is very difficult. In RSA, the public key is generated by multiplying two large prime numbers and  together, and the private key is generated through a different process involving  and . A user can then distribute his public key , and anyone wishing to send the user a message would encrypt their message using the public key. Algorithm of RSA :- Choose two large prime numbers P and Q such that P is not equals of Q. Calculate ...

what is Data Encryption Standard (DES)? Data Encryption Standard (DES) is a symmetric-key algorithm for the encryption of data.It is a outdated method for encrypting data.It uses a single private key for encryption and decryption of data.Data Encryption Standard (DES) is published by the National Institute of Standards and Technology (NIST).Data Encryption Standard (DES) is a block cipher it means that the data we do encrypt is encrypted in form of blocks. In DES we have a 64 bit plane text which converts into 64 bits cipher text after do DES encryption.