Different Types of SQL Server Functions

Types of Function

1. System Defined Function

   These functions are defined by Sql Server for different purpose. We have two types of system defined function in Sql Server

   1. Scalar Function

      Scalar functions operates on a single value and returns a single value. Below is the list of some useful Sql Server Scalar functions.

      abs(-10.67)-

      This returns absolute number of the given number means 10.67.
      rand(10)-

      This will generate random number of 10 characters.

      round(17.56719,3)-This will round off the given number to 3 places of decimal means 17.567

      upper(‘dotnet’)-This will returns upper case of given string means ‘DOTNET’

      lower(‘DOTNET’)-This will returns lower case of given string means ‘dotnet’

      ltrim(‘ dotnet’)-This will remove the spaces from left hand side of ‘dotnet’ string.

      convert(int, 15.56)-This will convert the given float value to integer means 15.

       

   2. Aggregate Function

      Aggregate functions operates on a collection of values and returns a single value. Below is the list of some useful Sql Server Aggregate functions.

      max()-

      This returns maximum value from a collection of values.
      min()-

      This returns minimum value from a collection of values.

      avg()-

      This returns average of all values in a collection.

      count()-

      This returns no of counts from a collection of values.

       

2. User Defined Function

   These functions are created by user in system database or in user defined database. We three types of user defined functions.

   1. Scalar Function

      User defined scalar function also returns single value as a result of actions perform by function. We return any datatype value from function.

      1. –Create a table
      2. CREATE TABLE Employee
      3. (
      4. EmpID int PRIMARY KEY,
      5. FirstName varchar(50) NULL,
      6. LastName varchar(50) NULL,
      7. Salary int NULL,
      8. Address varchar(100) NULL,
      9. )
      10. –Insert Data
      11. Insert into Employee(EmpID,FirstName,LastName,Salary,Address) Values(1,’Mohan’,’Chauahn’,22000,’Delhi’);
      12. Insert into Employee(EmpID,FirstName,LastName,Salary,Address) Values(2,’Asif’,’Khan’,15000,’Delhi’);
      13. Insert into Employee(EmpID,FirstName,LastName,Salary,Address) Values(3,’Bhuvnesh’,’Shakya’,19000,’Noida’);
      14. Insert into Employee(EmpID,FirstName,LastName,Salary,Address) Values(4,’Deepak’,’Kumar’,19000,’Noida’);
      15. –See created table
      16. Select * from Employee

      

      1. –Create function to get emp full name
      2. Create function fnGetEmpFullName
      3. (
      4. @FirstName varchar(50),
      5. @LastName varchar(50)
      6. )
      7. returns varchar(101)
      8. As
      9. Begin return (Select @FirstName + ‘ ‘+ @LastName);
      10. end

      

      1. –Calling the above created function
      2. Select dbo.fnGetEmpFullName(FirstName,LastName) as Name, Salary from Employee

      

   2. Inline Table-Valued Function

      User defined inline table-valued function returns a table variable as a result of actions perform by function. The value of table variable should be derived from a single SELECT statement.

      1. –Create function to get employees
      2. Create function fnGetEmployee()
      3. returns Table
      4. As
      5. return (Select * from Employee)

      

      1. –Now call the above created function
      2. Select * from fnGetEmployee()

      

   3. Multi-Statement Table-Valued Function

      User defined multi-statement table-valued function returns a table variable as a result of actions perform by function. In this a table variable must be explicitly declared and defined whose value can be derived from a multiple sql statements.

      1. –Create function for EmpID,FirstName and Salary of Employee
      2. Create function fnGetMulEmployee()
      3. returns @Emp Table
      4. (
      5. EmpID int,
      6. FirstName varchar(50),
      7. Salary int
      8. )
      9. As
      10. begin
      11. Insert @Emp Select e.EmpID,e.FirstName,e.Salary from Employee e;
      12. –Now update salary of first employee
      13. update @Emp set Salary=25000 where EmpID=1;
      14. –It will update only in @Emp table not in Original Employee table
      15. return
      16. end

      

      1. –Now call the above created function
      2. Select * from fnGetMulEmployee()

      

      1. –Now see the original table. This is not affected by above function update command
      2. Select * from Employee