#Sql decode series

I hope this article has given you more clarity on these three functions and which one to use. You could use COALESCE to perform advanced logic, but I would suggest using the function for its intended use, and using CASE for your advanced logic.

#Sql decode series

CASE is better than DECODE because it is easier to read, and can handle more complicated logic.Īs far as performance goes, there is minimal difference between CASE and DECODE, so it should not be a factor in your decisions.įor simply transforming a series of NULL values, I would suggest using COALESCE. I would suggest using CASE in almost every case. They also handle NULL values differently. More keywords within the statement allow you to break up the logic, rather than using a series of parameters in a single function. Tasks that are hard to implement with DECODE are easy to implement using CASE, which makes it easier to write your SQL. It was introduced into Oracle to replace the DECODE function.ĬASE offers more flexibility than the DECODE function. The ELSE keyword specifies what happens if no condition is met. Many conditions and results can be specified, and if a condition matches the expression, then the result is returned. The expression is used to compare against. The CASE statement in Oracle isn't a function, so I haven't labelled it as one.ĬASE allows you to perform IF-THEN-ELSE logic in your SQL statements, similar to DECODE. It can handle advanced logic, but can get hard to read as the function gets longer. The DECODE function is an older function, but still quite powerful. Search is compared against the expression, and if it is true, then result is returned.

Many combinations of search and result can be supplied. The syntax is: DECODE ( expression, search, result. The DECODE function in Oracle allows you to have IF-THEN-ELSE logic in your SQL statements. It can't change other values, such as 0, or advanced logic compared to CASE and DECODE. The downside is that it only transforms NULL values. It's better than using an NVL function as it takes more parameters, which may be more useful for your code. If expr is null, then Oracle returns the result of the first search that is also null. It's a simple function, and it's helpful as it can take a lot of parameters, and it's easier to write. In a DECODE function, Oracle considers two nulls to be equivalent. Many expressions ( expr1, expr2) can be used. The syntax is: COALESCE ( expr1, expr2, ) The Oracle COALESCE function allows you to return the first non-NULL value from a list of parameters Which one should you use? I'll explain the pros and cons of each in this article. They can transform a value into another value. Let’s take some examples of using the DECODE() function to see how it works.The Oracle functions CASE, DECODE, and COALESCE all perform similar functionality. In other words, the DECODE() function never evaluates a search (si+1) when a previous search (si) equals e. The following illustrates the syntax of the SQL DECODE()function: In this syntax: 1. , or sn) only before comparing it to the first argument (e), rather than evaluating all search values. The DECODE() function evaluates each search value (s1, s2.

You can use expressions for the search (s), the result (r), and default value (d) in the DECODE() function. The DECODE() function returns a value with the data type of the first result (r1, r2. dĭ is an expression to return when e does not equal to any searched value s1, s2. The r1, r2, …, or rn is the expression to return when e is equal to s. Note that s2, s3, … sn are automatically converted to the data type of s1 before comparing.

The s1, s2, … or sn is an expression to search for. The function automatically converts e to the data type of s1 before comparing.

The first argument e is the value to be searched. , ) Ĭode language: SQL (Structured Query Language) ( sql ) Arguments e