Oracle practice 2

Skills for using decode () functions in Oracle
Description:

Decode(Condition, value 1, translation value 1, value 2, translation value 2,... value n, translation value n, default value)

The function has the following meanings:

If condition = value 1 then
Return (translation value 1)
Elsif condition = value 2 then
Return (translation value 2)
......
Elsif condition = value n then
Return (translation value n)

Else
Return (default)
End if

1. Compare the size

SelectDecode(Sign (variable 1-variable 2),-1, variable 1, variable 2) from dual; -- smaller value
The sign () function returns 0, 1, and-1 respectively based on a value of 0, positive, or negative.
2. Calculate and count the monthly sales performance (sometimes it can be used for row-column conversion)
Reference statement:
Select sum (decode (substrb (month, 5, 2), '01', hour, 0), sum (decode (substrb (month, 5, 2), '02', hour, 0), sum (decode (substrb (month, 5, 2), '03', hour, 0) from sale;