Types of User Defined Functions in SQL Server Database

A database is a collection of data that has got some rules to manipulate the data and data models stored in it. SQL is a special-purpose computer programming language intended to deal with the data entered into in a relational database management system often abbreviated as RDBMS. A database server is a PC program that gives database administrations to different projects or PCs, as characterized by the customer server commands. Accordingly, a SQL Server is a database server that executes the Structured Query Language (SQL).

Today, we will discuss the concept of Function in SQL Server and various other aspects that are associated with it such as its types, advantages of user-defined functions etc.

Let us first begin by talking about “Functions”

What is Function in SQL server?

A function, in general, is a programming unit returning output by a single value command, enabling the values to be passed in as parameters. The parameters can change the result or restore the after effect of the given function. The magnificence of a function is that it is independent and would thus be able to be implanted in an expression.

A function is a database object used in a SQL Server. Fundamentally it is an arrangement of SQL statements whose role is to acknowledge the information parameters, perform activities and return the outcome when needed. The function can return only a single value or a table. We can’t utilize function to Insert or Update or Delete the records already stored in the database table(s).

Popular types of SQL Server functions

There are primarily two types of functions in SQL Server which are then further sub-divided as follows:

  • System Functions: All the implicit functions upheld by the SQL are called as System Functions. We don’t need to pay much of a heed to the logic that is working inside them since they can’t be changed at all. Some good examples of the same are- Ranking Functions, Mathematical Functions, String Functions, et cetera.
  • User Defined Functions: SQL Server enables us to make our own functions called as user-defined functions. For instance, on the off chance that we need to play out some knotty complex computations then we can put them in a separate function, and store it in the database. At whatever point we require those computations, it becomes easy as we can call it anytime.

There Are Two Sorts of SQL User-Defined Functions

  • Scalar Function:It is a function that is most typically used for returning a single value. For the most part, we need to characterize the function body between BEGIN … END square yet for the inline scalar function you can discard them. We can utilize any SQL data type as the return type with the exception of image, text, ntext, cursor, and timestamp.
  • Table Valued Functions:It is a function that has got the ability to return a table.
    • Inline Table-valued Functions: This function returns a table data type in light of a single command of SELECT Statement.
    • Multi-Statement Table-valued Functions: This function also likewise returns the tabular result which is set the forbidden outcome but at the same contrasting the inline table-valued function we can utilize different select statements within the function body.

Advantages of User-Defined Functions in SQL Server

User-Defined functions are helpful in the following ways-

  • Extensible Programming: You can generate the function once, store it in the database, and then call it for any number of times in your defined program. User-defined functions can be adjusted irrespective or you can say independent of the source code program.
  • Agile Implementation: Just like the stored techniques, Transact-SQL user-defined function lessens the assemblage cost of Transact-SQL code by storing the plans and reusing them for rehashed executions. This implies that the user-defined function does not require be reparsing and reoptimizing with each utilization that happens to bring about the considerably quicker execution time.
  • Reduced Network Traffic: A task that channels information in view of some complex requirement that cannot be communicated in a single scalar articulation can be very easily expressed as a function. The function would then be able to summon the WHERE clause in a function statement to decrease the number of lines sent to the end customer.

Some Guidelines with respect to SQL Server Functions

Transact-SQL errors that are the reason that a statement has to be dropped and one needs to proceed with the following statement in the module, (for example, triggers or any stored strategies) are dealt with differently inside a function. In functions, such mistakes make the execution of the function to stop. Because of this, the statement that had summoned the function is also wiped out.

The statements in a BEGIN…END piece can’t have any side effects. Function side-effects are any perpetual changes to the condition of an asset that has a scope outside the function, for example, an adjustment to a database table. The main changes that can be put forth by the expressions in the function are changes to objects local to the function, for example, nearby cursors or factors. Changes to database tables, activities on cursors that are not nearby to the function, sending email, endeavoring a list alteration, and creating an outcome set that is returned to the client are the cases of activities that can’t be performed in a function.

The actual number of times which a function specific to an inquiry is actually implemented can depend on the execution plans built by the optimizer. An example is a function summoned by a subquery in a WHERE clause of the statement. The real number of times this subquery is executed can fluctuate with the difference in access ways picked by the streamlining agent of your SQL server.

Types of valid statements in a SQL Server Function

The following are the types of statements that are valid in a function of SQL Server

  • DECLARE statements can be utilized to characterize information factors and cursors that are neighboring the function.
  • Assignments of values to objects neighboring to the function.
  • Cursor operations that duly reference neighboring cursors that are pronounced, opened, shut, and deallocated in the function. FETCH statements that return the information to the customer are not permitted. Just FETCH statements that allot values to neighboring factors utilizing the INTO clause in the statement are permitted.
  • Control-of-flow statements with the exception of TRY…CATCH statements.
  • SELECT statements containing select records with statements that allot values to factors that are nearby to the function.


We hope that the article was informative and you got answers to the subject you were looking for. The article more or less covers everything that was to be told about Functions in SQL Server.

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