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Use of the DECODE Function in SQL 

When you belong to the programming world or are fond of programming languages, you must be aware of SQL. The world of programming is broad, and there are numerous elements that one needs to know about when dealing with the world of programming. One of the significant and beneficial components is the DECODE function in SQL. The following discussion will discuss the functionality of the DECODE function in SQL. So, look through the discussion below to understand the use of the DECODE function and its importance in SQL.

What is SQL?

Before we begin with the main aspect of the discussion, let us first have a clear idea about what SQL is. The term SQL is for Structured Query Language and is a domain-specific language. It finds its utility in programming. It has been designed to manage data that are held in the relational database management system. And it also finds its utility for stream processing tasks in relational data stream management systems. It belongs to the family query language.

 Its primary function is to enable the users to communicate with a database. The American National Standards Institute states SQL is the standard language for relational database management systems. 

What is the DECODE function?

The DECODE function generally compares each expression 2 with expression 1. when expression 1 equals expression 2, or both are null, the expression value is returned. When expression 2 does not match with expression 1, the value of the else-expression gets returned in such cases. In the other cases, a null value gets returned. It is essential to understand the basic functioning of the DECODE function.

 The scheme that functions here is known as SYSIBM. The DECODE function has certain similarities with the CASE expression. The exception is the act of how the DECOR functions and deals with the bulls.

Here are the different ways in which the DECODE function deals with the null values

●  A null value in expression 1 will match a null value in expression 2 where the former will correspond with the latter.

●  When the NULL keyword is used as an argument in the DECODE function, it should be cast to a data type suitable for the comparison aspect.

Here is an important part that you must consider. An argument of DECODE should not repress any array value. The regulations for establishing the result type of the results for this function are based on the corresponding CASE expression. Here are some examples that can assist you ideally.

Examples of DECODE function equivalent of CASE expression

DECODE function: DECODE(c1, 7, ‘a’,

  6, ‘b’, ‘c’)

 CASE expression: CASE c1

  WHEN 7 THEN ‘a’

  WHEN 6 THEN ‘b’

  ELSE ‘c’


DECODE function: DECODE(c1, var1, ‘a’,

  var2, ‘b’)

 CASE expression: CASE

WHEN c1 = var1 OR

         (c1 IS NULL AND

var1 IS NULL) THEN ‘a’

WHEN c1 = var2 OR

         (c1 IS NULL AND

var2 IS NULL) THEN ‘b’




The function of DECODE in SQL is quite important and beneficial, and the above discussion has ideally explained it to you. Now, you can readily use this function to carry out your necessary programming tasks on SQL. To learn more, visit Education Nest.

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