[Oracle] Functions

String Functions

Lower (char) to lowercase
Convert upper (char) to uppercase
Length (char) returns the length of the string.
Substr (char, m, n) truncates a string, the position starting from M (starting from 1), and the length of N.

Replace (char1, search_string, replace_string)
Instr (char1, char2 [, N [, m]) obtains the position of the string

Mathematical functions
Round (N [, m]) Rounding
Trunc (N [, m]) truncates a number
MoD (m, n) modulo
Floor (n) returns the largest integer less than or equal to n.
Ceil (n) returns the smallest integer greater than or equal to n.

Date Functions
Sysdate returns the system time
Add_months (d, n)
Last_day (d) returns the last day of the month of the specified date.

Conversion functions
To_char

Hh24
Hh12
Mi
SS

9: displays numbers. Ignore the preceding 0.
0: displays numbers. If not, use 0 to complete
.: Display the decimal point at the specified position
,:
$: Add US dollars before the number
L: Local Currency
C: International Currency
G: display the separator at the specified position
D: display the decimal point at the specified position

System Functions
Select sys_context ('userenv', 'db _ name') from dual;