Use case when in oracle query statements

In the oracle query statement, the use case when statement Syntax of case when is as follows: case when expression then valueA else valueB end; the specific use is as follows: select (case when. column1> = 1 then' success 'else' failure 'end) as Success_flag from tableA if. if the value of column1 is greater than or equal to 1, the value of Success_flag will be 'successful'; otherwise, 'failed '. The usage of case when and decode functions is similar, but decode is an enumeration function, while case when is more flexible. At the same time, case when is equivalent to a special function with only two enumeration values. Case when is mostly used to compare the size of two values. It is more flexible than least (take a smaller value) and greatest (take a smaller value) when comparing values. For example, selectleast (1, 2), greatest (3, 4) from dual; the query result is 1 4.