Oracle character functions

UPPER (char) lowercase to uppercase

LOWER (char) uppercase to lowercase

Initcap (char) First letter conversion

SUBSTR (Char,[m[,n]]) to intercept string functions
Start interception from the source string char m, intercept n bits you can omit, represent intercept to the end
M is 0, which means the first letter of the punch string is truncated. M is a negative number, indicating the trailing intercept of the punch string
Example:
Sql> Select substr (' ABCDE ', 2,3), substr (' ABCDE ', 2), substr (' ABCDE ', -2,1) from dual;

SUB SUBS S
--- ---- -
BCD BCDE D

Sql> Select substr (' ABCDE ', 2,3), substr (' ABCDE ', 2), substr (' ABCDE ', -2,2) from dual;

SUB SUBS SU
--- ---- --
BCD Bcde de

Length (char) to get string lengths

CONCAT (CHAR1,CHAR2) string Join function
with | | The function of the operator is the same

To remove a substring function:
TRIM (C2 from C1)
This function represents the removal of characters from the string C1 c2

TRIM (C1)
Trim has only one parameter, which represents the trailing and trailing spaces

Remove from head
RTRIM (C1[,C2])
Remove from tail

Replace (char,s_string[,r_string]) Replacement function

Instance:
sql> Select replace (' abced ', ' a ', ' a ') from dual;

Repla
-----
abced

sql> Select replace (' abced ', ' a ') from dual;

Repl
----
bced

sql> Select replace (' abced ', ' ab ', ' A ') from dual;

Repl
----
aced

Oracle character functions