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How to Use Alter, Drop, Rename, Aggregate Function in SQL Server?


Welcome to the world of SQL Server and its powerful functions! Data has become integral to every business in today’s digital era. For years, people have used SQL Server, a relational database management system, to manage and store their data. 

One of the key features that make SQL Server so powerful is its ability to handle complex tasks through its functions. Functions in SQL Server are a set of SQL statements that perform a specific job, promoting code reuse and improving efficiency. With the help of functions, you can accomplish the same action repeatedly without writing lengthy SQL scripts. 

In this blog, we'll look at the many kinds of functions that SQL Server offers and how they might make coding easier. Let's explore the SQL Server functions now!

  • To create a function in T-SQL, like a SELECT statement
  • To call a function in applications
  • To define a function within another user-defined function
  • To define a column in a table
  • To parametrize or improve the functionality of an indexed view.
  • To determine the check constraint on a column
  • To replace some stored procedure
  • To set the filter predicate using the INLINE function for security purposes.

What Is Sql Server?

Before learning about types of functions in sql server, you must also understand what is sql server afterall?

Microsoft created the relational database management system (RDBMS) SQL Server. It is used to organize data storage and management, and it supports SQL (Structured Query Language) for data management and querying.

Small-scale apps and large-scale enterprise systems use SQL Server in various applications and sectors. Data encryption, backup and recovery, replication, and reporting services are just a few of its services.

C++, C#, Java, Python, and other programming languages are supported by SQL Server. It is a frequent choice for managing massive, data-intensive systems and is widely used in web development, corporate analytics, and data warehousing.

What Are The Features Of Sql Database?

SQL databases are within the group of database management systems known as relational database management systems (RDBMS), which employ SQL for data administration and querying. It is widely utilized in various applications, from modestly sized programs to massive business systems. Following are some of the primary characteristics and applications of the SQL database:

  1. Data Integrity: Referential integrity constraints, unique constraints, and other constraints are enforced by the SQL database to guarantee data integrity. This feature ensures the reliability, consistency, and accuracy of the data. Also, it aids in minimizing data duplication and preserving data consistency.
  2. Scalability: The SQL database is very scalable and can effectively handle a large amount of information. It can expand horizontally or vertically, adding extra resources to a single server (adding more servers to the system). This functionality enables enterprises to manage the expanding data volume without sacrificing performance.
  3. Security: The SQL database has robust security measures to guard against intruders accessing data, data breaches, and other security risks. It provides user authentication, access control, data encryption, and auditing attributes. Sensitive data is protected and secured by these features. SQL databases provide backup and recovery functions to safeguard data from being lost due to hardware failure, software defects, or other unanticipated circumstances. Businesses can rapidly and effectively recover from data loss thanks to this functionality.
  4. Data Replication: SQL database options for replicating data across numerous servers or data centers are available. This function aids in increasing data accessibility and reducing the chance of data loss.
  5. Support for XML: The SQL database provides XML data support, utilized in many applications, such as data exchange, online services, and e-commerce. It offers tools for storing, querying, and working with XML data.
  6. Support for Spatial Data: The SQL database provides efficient storage and manipulation of spatial and geographic data. It offers tools for storing, indexing, and querying spatial data, which is utilized in many different contexts, such as geolocation and mapping.

Types Of Functions In Sql Database

SQL Functions are programs either developed by the user or already provided by the SQL Server system which can be used to perform certain repetitive tasks.

System-Defined Function 

“System-specified functions” are the functions that the system defines. In other words, system-defined functions refer to all the built-in SQL server functions supported. These functions typically use the SQL select statement to calculate the values and handle the data. Using the built-in features allows for significant development time savings when carrying out specific activities.

User-Defined Function 

“User-defined functions” are often referred to as “functions that are developed by the user or developer in the system database or a user-defined database.” The user-defined functions may consider necessary parameters, carry out specific tasks, and return the data that has been processed. 

By encapsulating the complex business logic and making it available for reuse whenever equivalent functionality is needed, these custom functions aid in the simplification of the database development process as a whole. 

The user-defined functions make it much simpler to build the code required to query data. Additionally, it enhances the functionality, clarity, and accessibility of queries and enables other developers to reproduce the same processes appropriately. User-defined functions are those that a database user defines. The two sorts of UDFs are:

  • Scalar functions: A scalar function is a function that only returns a single data value.
  • Table-valued functions: A table-valued function is a function that returns many records as a table data type. It might be a single-choice statement’s result set.

Best Practices For User-Defined Function In Sql Server

In order to use the uder-defined functions in sql server, you must know the correct syntax and practices for your functions to run smoothly. There are many top best-rated SQL books for beginners and advanced learners that talks about the usage of SQL functions in length. Here are some of the best practices compiled that must be followed: 

  • Function names should always comply with the rules of identifiers.
  • Use a schema-binding clause within your function to keep the data secure.
  • The function’s name should be clear to both the user and the developer.
  • You can define up to 2100 parameters for a particular function.
  • Don’t forget to add data types based on the nature of the value you want to store.
  • The scope of functions is generally defined locally, so tasks with the same name can be used in other programs or applications too. The same case is valid for parameters defined within functions

You cannot alter, drop, rename, or aggregate a function if it is not created. To drop a function in SQL, you either need to ALTER permission on the Schema to which the process belongs or CONTROL permission on the function. To re-create a function, CREATE FUNCTION permission and ALTER approval on the Schema in which the function is created. With this discussion, you know how to make a function in T-SQL. Now let us discuss how to alter, drop, rename, and aggregate SQL functions.

How To Rename User-Defined Functions In Sql Server ?

To rename a function SQL Server, you can use either SQL server management Studio or Transact-SQL. When you rename a user-defined function, it will not change the corresponding object name in the definition of a function. So, it would be best if you dropped or recreated a function in that case instead of renaming it. Also, changing the name of the user-defined function can affect the performance of the attached objects too. 

The dependent things may stop working when the function is loaded again. Let us see how to rename a user-defined function in SQL SERVER MANAGEMENT STUDIO.

  • To rename an object, click on the plus sign next to the database that contains the function and rename it.
  • Now click on the plus sign next to the Programmability Folder.
  • Click on the plus sign next to the function you wish to rename. It could be a table-valued function, a scalar-valued function, an aggregate function, etc.
  • Please right-click on the function now and Rename it.
  • Give a new name to the function, and you are good to go.

This method cannot be used for the T-SQL database. To rename a T-SQL function, you first have to delete it and recreate it with the new name. Ensure that app applications and programs using the older function are now connected with the new one.

How To ALTER A Function In Sql Server?

Here, we will learn how to ALTER a function created using the CREATE statement by changing its permission and affecting the dependent functions, stored procedures, triggers, etc. Here is the basic syntax for the ALTER command in SQL.

ALTER command cannot be used to change a T-SQL function to a CLR function or vice versa. ALTER function cannot be used to change a scalar-valued function to a table-valued function. Also, ALTER function cannot be used to change the INLINE function with multiple statements.

How To DROP A Function In SQL Server?

As we discussed, functions are created using the CREATE function and modified using the ALTER function. The DROP command is valid for existing functions only. The basic syntax for the drop command is given below.

Here, you can add the schema name to which the function belongs and the name of a user-defined function to be removed. Adding the schema name is optional, but the server name or database name cannot be specified here. DROP function does not work if it is bound with a Schema binding clause. It will not work if computed columns that reference this function are indexed. To execute the DROP function, you should add ALTER permission on the Schema to which it belongs or CONTROL permission on the function.

How To Use An Aggregate Function In Sql?

An aggregate function calculates a set of values and returns a single value. An aggregate function is generally used with the GROUP BY clause of the SELECT statement. It ignores null values too. They are deterministic and return the same value every time they are called for a specific set of inputs. There are certain cases where the aggregate function should be used as an expression. There are multiple aggregate functions in SQL, and you may use any one based on requirements. A complete range of aggregate functions in SQL is given below.

Similarly, SQL offers a complete range of in-built functions to perform operations on data. They are useful for mathematical calculations, string concatenation, sub-strings, etc. Each has a different syntax and is generally picked based on the analysis you want to perform with a function. If they are not used correctly, the final output differs from your expectations. So, it is necessary to understand the function of SQL Server and learn to use them effectively with basic syntax and argument knowledge.

What advantages do user-defined functions offer?

  1. Unlike stored procedures, they can be used anywhere without constraints.
  2. It is possible to simplify, and it makes code easier.
  3. The function can accept parameters.
  4. They can be used in a select, where, or case statement and to build joins.
  5. Easy to use.
  6. Faster Execution: Just like stored procedures, UDFs speed up T-SQL execution by caching the execution plans and reusing them during subsequent runs.
  7. Reduce Network Traffic: When a function is called, the application must make a function call to the database, where the SQL queries for the function are executed.
  8. UDFs can be changed independently of the application source code, supporting modular programming. 
  9. UDFs can be created once, stored in the database, and called as many times as necessary

Advantages of SQL Server

Microsoft’s relational database management system (RDBMS), SQL Server, has several benefits, including:

  • High-performance data processing features, such as quick data retrieval and transaction processing, are provided by SQL Server. Additionally, it has sophisticated indexing and query optimization tools that let it efficiently manage massive amounts of data.
  • Scalability: Because SQL Server is made to scale from small businesses to giant corporations, it is the perfect answer for firms that need to manage to expand data volumes.
  • Security: To prevent data from unwanted access, SQL Server has robust security features like authentication, authorization, and encryption.
  • Effortless integration of SQL Server with other Microsoft products, including Visual Studio, SharePoint, and Excel, makes developing and maintaining data-driven applications simple.
  • Reporting Services, Analysis Services, and Integration Services are just a few of the business intelligence capabilities included in SQL Server that enterprises may use to evaluate and better utilize their data.
  • Cloud Integration: SQL Server can be set up on the cloud, giving businesses access to its scalability and cost-efficiency while reaping the rewards of a reliable RDBMS.
  • Support: Many resources are available for help, including manuals, forums, and user groups, due to the widespread use of SQL Server and the sizable development and user community. Microsoft also provides qualified support for SQL Server.


SQL database offers a range of features essential for managing and storing data efficiently. It is the best option for enterprises of all sizes because of its scalability, security, and backup and recovery options. Its reporting services, full-text search, and XML support features make it popular for web development and e-commerce applications. Its spatial data support feature makes it an essential tool for mapping and geolocation applications. To know more about SQL database, join our sql dba training to gain hands-on experience in working with real-world projects and be industry ready!


Q1. What are different types of SQL functions?

A1. In SQL Server, there are three types of user-defined functions

  • Scalar functions (those that return a single value)
  • Table Valued Functions (a single TSQL command that returns a Table Set)
  • Table Valued Functions with numerous Statements (contains numerous TSQL statements and returns a Table Set)

Q2. How to get all functions in SQL Server?

You may use the transact SQL command on system objects such as Sys. Objects, Information_Schema. Routines, syscomments, or Sys. Sql_Modules to retrieve a list of all the functions in a database.

Q3. What is the syntax for function in SQL Server?

To construct a function in SQL Server (Transact-SQL), use the following syntax: 

CREATE FUNCTION [schema_name.] function_name ( [ @parameter [ AS ] [type_schema_name.] datatype [ = default ] [ READONLY ] , @parameter [ AS ] [type_schema_name.]

Q4. What is schema in SQL?

A schema is a list of logical data structures in a SQL database. The schema, which has the same name as the database manager, is owned by a database user. As of SQL Server 2005, a schema is a separate entity (container of objects) from the person who creates the item.

Q5. How many aggregate functions are there in SQL?

There are five aggregate functions in SQL,. These functions are as follows: MIN, MAX, COUNT, SUM, and AVG.

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