Purpose
UPPER() converts all letters in a string to uppercase.
Syntax
UPPER(char)
Parameters
char is the string to be converted. It can be of the CHAR, VARCHAR2, NCHAR, NVARCHAR2, or CLOB data type.
Return type
The return type is the same as the data type of char.
Examples
The following example converts all letters in the string OceanBase to uppercase.
obclient> SELECT UPPER('OceanBase') "UPPER" FROM DUAL;
+-----------+
| UPPER |
+-----------+
| OCEANBASE |
+-----------+
1 row in set