Casting Data Type in Oracle Database

CAST function 
The CAST function converts a value from one data type to another data type.

Syntax
CAST ( [ Expression | NULL | ? ] AS Datatype)

Note : CAST conversions among SQL-92 data types.
The flowing are SQL-92 data types

1. BOOLEAN
2. SMALLINT
3. INTEGER
4. BIGINT
5. DECIMAL
6. REAL
7. DOUBLE
8. FLOAT
9. CHAR
10. VARCHAR
11. LONG VARCHAR
12. CHAR
13. VARCHAR
14. LONG VARCHAR
15. CLOB
16. BLOB
17. DATE
18. TIME
19. TIMESTAMP
20. XML

Examples
SELECT CAST (SYSDATE AS VARCHAR2 (12)) DATE_TO_VARCHAR FROM DUAL;
SELECT CAST ('12' AS INTEGER)  STRING_TO_NUMBERIC FROM DUAL;
SELECT CAST (NULL AS VARCHAR2 (2)) NULL_TO_STRING FROM DUAL;

As CAST only convert among SQL-92 data types, we can not use for example RAW data type.
But there are some packages casts to RAW like utl_raw.cast_to_raw

SELECT UTL_RAW.CAST_TO_RAW('Mahmoud') FROM DUAL;
output is : "4D61686D6F7564"