The commonly used string functions include LENGTH, SUBSTR, CONCAT, UPPER, LOWER, LTRIM, RTRIM, and TRIM.
Note that in an Oracle tenant, the LENGTH function calculates string length using characters and the LENGTHB uses bytes, as defined by the character set. For example, calculating the string length of the word "medium":
obclient> select length('medium'), lengthb('medium') from dual;
+---------------+----------------+
| LENGTH('medium) | LENGTHB('medium') |
+---------------+----------------+
| 1 | 3 |
+---------------+----------------+
1 row in set (0.00 sec)
obclient> select * from sys.nls_database_parameters where parameter='NLS_CHARACTERSET';
+------------------+----------+
| PARAMETER | VALUE |
+------------------+----------+
| NLS_CHARACTERSET | AL32UTF8 |
+------------------+----------+
1 row in set (0.01 sec)