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.
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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. Get Mastering Oracle SQL now with the O’Reilly learning platform. I would suggest using CASE in almost every case. We can do that with DECODE: SELECT SUM (DECODE (TOCHAR (orderdt, 'Q'), '1', saleprice, 0)) Q1, SUM (DECODE (TOCHAR (orderdt, 'Q'), '2', saleprice, 0)) Q2, SUM (DECODE (TOCHAR (orderdt, 'Q'), '3', saleprice, 0)) Q3, SUM (DECODE (TOCHAR (orderdt. 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. The s1, s2, or sn is an expression to search for. The function automatically converts e to the data type of s1 before. The first argument e is the value to be searched. Search is compared against the expression, and if it is true, then result is returned. Oracle DECODE () function syntax Arguments. 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.
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, en) Code language: SQL (Structured Query Language) (sql) In this syntax, the COALESCE () function returns the first non-null expression in the list. The syntax for the DECODE function in Oracle/PLSQL is: DECODE ( expression, search, result, search, result. The downside is that it only transforms NULL values. The following illustrates the syntax of the Oracle COALESCE () function: COALESCE (e1, e2. It's better than using an NVL function as it takes more parameters, which may be more useful for your code. It's a simple function, and it's helpful as it can take a lot of parameters, and it's easier to write. 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. Examplesįrom MariaDB 10.3.The Oracle functions CASE, DECODE, and COALESCE all perform similar functionality. If no matches are found, the default expression is returned, or NULL if no default is provided.ĭECODE_ORACLE is a synonym for the Oracle-mode version of the function, and is available in all modes. If it finds a match, the corresponding result expression is returned. In Oracle mode from MariaDB 10.3.2, DECODE compares expr to the search expressions, in order. s1, s2,, or sn is the expression to search for. , ,sn,rn, d) Code language: SQL (Structured Query Language) (sql) In this syntax: e is the argument that to be searched for or compared with other argument s1, s2, sn. The resulting string will be the original string only if pass_str is the same. The following illustrates the syntax of the SQL DECODE () function: DECODE (e, s1, r1, s2, r2. crypt_str should be a string returned from ENCODE(). In the default mode, DECODE decrypts the encrypted string crypt_str using pass_str as the In all modes from MariaDB 10.3.2: DECODE_ORACLE(expr, search_expr, result_expr ) In Oracle mode from MariaDB 10.3.2: DECODE(expr, search_expr, result_expr )
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