Can anyone please explain the below SQL statement from Oracle DB:
select decode(TRIM(to_char(SYSDATE,'Day')),'Monday','3','1') from dual
First of all, let's start with the
to_char(SYSDATE,'Day') will give you the day of the week it is today.
to_char lets you convert a date (in this case today's date since you've specified
sysdate) into a string of a certain format. Take a look here for some other examples of date formats you can use:
trim removes leading and trailing whitespace.
Now for the
decode. You can think of
decode like an if else statement. Take a look at:
In your particular example, you could read this statement as: if today is Monday return 3 else return 1.
decode also allows you to do things a bit more complex like this:
select decode(TRIM(to_char(SYSDATE,'Day')),'Monday','3','Tuesday',5,'1') from dual
This would read: if today is Monday return 3, else if today is Tuesday return 5, else return 1