Functions In SQL | Tables, Keys, Triggers, Procedures, Views, and User-Defined Objects.

What are SQL server objects? Besides tables and keys, can you have any other objects? What are user-defined functions, and how many types of functions can you get in SQL?

If you are into programming, these questions must have crossed your mind. To use the SQL language effectively, you need to understand and familiar with the different types of functions, their function name, and how to write them in SQL with the correct format and command. Our online SQL courses reviews can help you when it comes to choosing the right course for you.

When creating user-defined objects in a database, some of the objects you can make are user-defined functions. If you use them appropriately, the functions prove to be powerful tools in your databases.

But what is SQL, and what functions are there in SQL?

SQL

SQL stands for Structured Query Language. It is a programming language that helps to manage the data you store in relational databases.

The SQL programing language operates through declarative and straightforward statements. The declarative statements help keep the data secure and accurate, and it also helps to maintain the integrity of databases, irrespective of their size.

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SQL Server Object 

If you are using the SQL programming language to create databases, you can create various objects that are on the database.

Some of the objects you can create include tables and keys. You can also develop other objects, including triggers, procedures, views, and user-defined objects.

The idea behind objects is to store them in the database and avoid writing the same code repeatedly.

SQL also controls what is in the output and defines the structure and type of output.

You can also define permissions for the functions to decide who can use them and in what way they can use them.

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How Many Types of Functions Are There in SQL? 

Imagine a situation where you are writing a complex query, and you have to add a series of values. How would you add up the values?

Well, there are various methods you can use to add the values.

For instance, you can add the values such as:

Select val1 +val2 + val3 from <Table name>.

While this particular method will work, it has some drawbacks. You may have a few values, and it might be easy to add them up using this method. But what happens when you want to add more values? Would you have to go back to the query and make changes?

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What about a complex situation where you have a statement such as the one above written more than once?

The other method you can use to write a complex query is by use of functions. The SQL server comes with many built-in functions that you can use if they serve your purpose.

For instance, for the example of the complex query above, you can use the SQL sum function. To frame the query using the SQL functions, you can do the following:

Select sum() from <Table Name>.

SQL allows you to develop or write your functions if the system-defined functions in SQL don't serve your purpose.

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What are SQL functions?

SQL functions are programs already provided by the system (system-defined) or programs that can be developed by the user (user-defined). They can further be categorized into two categories, which include aggregate functions and scalar functions. Aggregate functions operate on many records and give a summary. The aggregate functions work with GROUP BY. On the other hand, scalar-valued functions (non-aggregate) work on each record independently.

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System Defined Functions 

System-defined functions refer to functions already developed in the system.

There are various types of system-defined functions, which include:

Aggregate Functions 

Aggregate functions are system defined functions that deal with numbers. The aggregate functions work on sets of rows and return results based on the group of rows.

Some examples of aggregate functions include:

  • SQL Count function: returns the number of rows and satisfies the criteria specified in the WHERE clause
  • SQL Avg function: it calculates the average value of a column in numeric type. It gives the average of all non NULL values
  • SQL Max function: is used to provide the highest value or maximum value of a particular expression or column. The max function is essential in determining the largest value in a column
  • SQL Min function: It helps find the lowest value or the minimum value in an expression or column. It is used to determine the smallest value of all the selected values in an expression or column
  • SQL Sum function: the aggregate sum function returns the sum of all the selected values in a column
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Arithmetic Function

An arithmetic function executes a mathematical operation based on input values provided as arguments and returns a numeric value as the result of the operation. Mathematical functions operate on numeric data such as integer, decimal, float, real, tinyint, and smallint.

Examples of arithmetic functions include:

  • abs()
  • floor()
  • mod()
  • power()
  • sqrt()
  • ceil()
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Character Function 

A character function is also known as a string function. It takes a character/characters or numbers as the parameters and returns a character value as a result.

Basic string functions provide various capabilities and return a string value as the result.

Examples of character functions include:

  • trim()
  • upper()
  • translate()
  • lower()
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Date Functions 

Date functions are system-defined functions related to dates.

Examples include:

  • GETDATE()
  • DATEADD()
  • Day()
  • Month()
  • Year()
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Advanced Functions

Advanced SQL functions perform a particular type of complex tasks like logical conditions.

Examples include:

  • CAST()
  • CONVERT()
  • CURRENT_USER()
  • ISNUMERIC()
  • IIF()
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User defined Functions

User-defined functions are divided into two categories, which include the scalar function and table-valued functions.

Scalar functions return a single value, while table-valued functions are functions that return more than one value.

Table value functions are further divided into two categories, including:

Inline table-valued function and Multi statement table-valued function.

The Inline table-valued function has a faster processing time, it includes only one statement, and it returns a table object as the output. On the other hand, the Multi statement table-valued function has a slower processing time, it includes multiple statements, and it returns a table variable as a result.

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Examples of SQL functions 

Examples of date function:

GETDATE()

Provides the current date.

select GETDATE()

DATEADD()

Select DATEADD (month, 1 , '20080628');

Add a month with the date value 20080628

Example of advanced function:

IIF()

An IIF function is used for the if-else condition in a single select statement.

e.g: select JobTitle,iif(Gender='m', 'MALE' , 'FEMALE' ) [GENDER] from [HumaResources] . [Employee]

The above query will give out FEMALE if the gender is female and MALE if the gender is male.

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Differences Between Procedures and Functions 

Procedures:

  • They cannot be called from a function
  • You cannot call a procedure within a procedure
  • For a procedure, it is optional to return a value
  • A procedure is compiled only once and executed again and again
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Functions:

  • A function can be called from a stored procedure
  • You can call a function within a function
  • You have to compile a function every time before execution
  • A function will always return value
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Conclusion 

If you want to find out what SQL functions are, our comprehensive guide makes the job easy for you. We have also explained various SQL functions and given a clear difference between system-defined functions and a user-defined function. 

You can also find out some examples of how you can enter the functions and the output you expect from the entry.

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