What is Function in Sql Server

A function is a block of code that has a name and it has a property that it is reusable. We use function in store Procedure and queries in sql server.

We can define function like-
 User Define function - It is created by user and use in any query and SP also.
 System Define function- Most of the function define by System in SQL inbuilt function.

SQL Function

Scalar Functions

Scalar functions is a function where it is return a single value. Below is the list of some useful Sql Server Scalar functions. UCASE()
LCASE()
ABS()
RAND()
ROUND()
UPPER()
LOWER()
LTRIM()
LEN()
FORMAT()
NOW()

SQL Aggregate Function

SQL Aggregate functions return a single value, calculated from values in a column.

    AVG()
   COUNT()
   SUM()
   MAX()
   MIN()

Detail Discription as below with example

AVG() - This function returns the average value of a numeric column in SQL Server.

SELECT AVG(columnName) FROM TableName

Example

SELECT AVG(Salary) AS Salary FROM Customer

We Create a Table Customer Insert Some Column Table look like as below -



Created Table Customer and we apply AVG of Salary in Customer table then use AVG function and easily find avg of salary like-

Note- In This Example Salary is ColumnName and Customer is TableName Find Avg of salary in customer table and see output as below-

COUNT() - This function is used to count total number of value and return total row in SQL Server.

SQL COUNT() Syntax-

        SELECT COUNT(columnName) FROM TableName

Example

SELECT COUNT(Salary) AS Salary FROM Customer

Note- In This Example Salary is columnName and Customer is TableName Return total num of salary in customer table and see output as below-

SUM() - This function is used to sum total number of value of the selected column  SQL Server.

SQL SUM() Syntax-

    SELECT SUM(columnName) FROM TableName

Example

SELECT SUM(Salary) AS Salary FROM Customer

Note- In This Example Salary is ColumnName and Customer is TableName Return Total SUM of salary in customer table and see output as below-

MAX() - This function returns the Max or largest value of the selected column in SQL Server.

SQL MAX() Syntax-

        SELECT MAX(columnName) FROM TableName

Example

SELECT MAX(Salary) AS Salary FROM Customer

Note- In This Example Salary is ColumnName and Customer is TableName Return Maximum salary in customer table and see output as below-

MIN() - This function returns the Minimum value of the selected column in SQL Server.

SQL MIN() Syntax-

      SELECT MIN(columnName) FROM TableName

Example

SELECT MIN(Salary) AS Salary FROM Customer

Note - In This Example Salary is ColumnName and Customer is TableName Return Minimum or smallest salary in customer table and see output as below-