SQL_CHR_ASCII_SUBSTR1
FYI: substring(start, lentgh),ASCII (value of a character), CHAR(character with ascii code/number) or CHR(character with ascii code/number)
ORACLE SQL: char() is chr() in Oracle

SELECT ENAME, SUBSTR(ENAME,1,1)"SBSTR1,1",CHR(ascii(ENAME))"CHR", ASCII(ENAME) "ASCII" FROM emp WHERE ROWNUM < 7

POSTGRESQL: char() is chr() in postgresql

SELECT ENAME, SUBSTR(ENAME,1,1)"SBSTR1,1",CHR(ascii(ENAME))"CHR", ASCII(ENAME) "ASCII" FROM emp LIMIT 6

MYSQL :chr() is CHAR in MySQL

SELECT ENAME, SUBSTR(ENAME,1,1)"SBSTR1,1",CHAR(ascii(ENAME))"CHAR", ASCII(ENAME) "ASCII" FROM emp LIMIT 6

 

char A-Z = 65-90, a-z= 97-122
Oracle:

PostgreSQL

MySQL