Function
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A function in SQL is a routine that takes parameters, performs an action, and returns a result, which can be a single value or a table. There are two main types of functions: user-defined functions (UDFs), which include table-valued and scalar-valued functions, and system-defined functions, which are predefined by SQL Server for specific purposes. Functions can only be used with select statements, must return a value, and do not support try-catch statements.
Function
- 1. A function is a Transact-SQL or common language runtime (CLR) routine that accepts parameters, performs an action, such as a complex calculation, and returns the result of that action as a value. The return value can either be a scalar (single) value or a table. The following is some important information about functions: Functions only work with select statements. Functions can be used anywhere in SQL, like AVG, COUNT, SUM, MIN, DATE and so on with select statements. Functions compile every time. Functions must return a value or result. Functions only work with input parameters. Try and catch statements are not used in functions. Types of Function: There is basically two tyes of functions in SQL server:- 1. User Defined Function These functions are created by user in system database or in user defined database. We two types of user defined functions. 1. Table Valued Function. 2. Scalar Valued Function.
- 2. 1.1 Table Valued Function In this type of function we select table data using a user created function. CREATE TABLE UserRegistration ( C_Id int IDENTITY(1,1) NOT NULL, C_Name varchar(100) NULL, C_Age varchar(100) NULL, C_Country varchar(100) NULL ); Now Insert records in UserRegistration Table :- Insert into UserRegistration(C_Name,C_Age,C_Country) values('Ramesh','27','India') Now we have to create one function like this: create function GetUserRecords() returns table as return(select * from UserRegistration) Now Call that function like this: select * from GetUserRecords() Note:This will return all records from table UserRegistration
- 3. 1.2 Scalar Valued Function: User-defined scalar functions return a single data value of the type defined in the RETURNS clause. For an inline scalar function, there is no function body; the scalar value is the result of a single statement. create function GetUserAge ( @name nvarchar(500) ) returns table As return ( select C_Age from UserRegistration where C_Name = @name ) Now call this function like this way select * from GetUserAge('Ramesh') For a multistatement scalar function, the function body, defined in a BEGIN...END block, contains a series of Transact-SQL statements that return the single value.
- 4. Create function MultistatementScalarFunction ( @name varchar(100), @Age varchar(100), @Country varchar(100) ) returns nvarchar(100) As Begin Return ( select (@name+'' +@Age+''+ @Country) ) End Now Call that function like this way: select dbo.MultistatementScalarFunction(C_Name,C_Age,C_Country)as Info from UserRegistration where C_Id=2 2.System Defined Function These functionsaredefined by Sql Server for differentpurpose. Wehave two types of system defined function in Sql Server 1. Scalar Function 2. Aggregate Function
- 5. 2.1 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. 2.1 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.