Oracle function decode

First, decode function

Meaning explanation:
1, Decode (condition, value 1, return value 1, value 2, return value 2,... Value N, return 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 (translated value N)
ELSE
RETURN (default value)
END IF

The result of this function is that when the value of the field or Field operation is equal to the value 1 o'clock, the function returns the value 2, otherwise the value 3
Of course, a value of 1, a value of 2, a value of 3 can also be an expression, this function makes some SQL statements a lot simpler

2, Decode (field or Field operation, value 1, value 2, value 3)

The result of this function is that when the value of the field or Field operation is equal to the value 1 o'clock, the function returns the value 2, otherwise the value 3
Of course, a value of 1, a value of 2, a value of 3 can also be an expression, this function makes some SQL statements a lot simpler

Second, add_months

Add_months has two parameters, the first parameter is the date, the second argument is the number (in months) that the date is added and minus

3 months later, select Add_months (sysdate,3) from dual;

3 months ago, select Add_months (sysdate,-3) from dual;

Third, case and then usage

Https://www.cnblogs.com/Richardzhu/p/3571670.html

Oracle function decode