Depending on specific storage format, constraints, and a valid range of column values, every column in Database have to define a particular type which is called Datatype.
Each value which is manipulated by Oracle Database has a data type. The data type of a value associates a fixed set of properties with the value. Using these properties Oracle treats values of one data type differently from values of another. For example, you can add values of NUMBER data type, but not values of CHAR data type.
Oracle Database provides a number of built-in data types as well as several categories for user-defined types that can be used as data types. Oracle provides the following categories of built-in datatypes:
The character datatypes store character (alphanumeric) data in strings, with byte values corresponding to the character encoding scheme, generally called a character set or code page.
The numeric datatypes store positive and negative fixed and floating-point numbers, zero, infinity, and values that are the undefined result of an operation (that is, is "not a number" or NAN).
The DATE datatype stores point-in-time values (dates and times) in a table. The DATE datatype stores the year (including the century), the month, the day, the hours, the minutes, and the seconds (after midnight).
Oracle Database can store dates in the Julian era, ranging from January 1, 4712 BCE through December 31, 9999 CE (Common Era, or 'AD'). Unless BCE ('BC' in the format mask) is specifically used, CE date entries are the default.
The LOB datatypes BLOB, CLOB, NCLOB, and BFILE enable you to store and manipulate large blocks of unstructured data (such as text, graphic images, video clips, and sound waveforms) in binary or character format. They provide efficient, random, piece-wise access to the data. Oracle recommends that you always use LOB datatypes over LONG datatypes. You can perform parallel queries (but not parallel DML or DDL) on LOB columns.
The RAW and LONG RAW datatypes are used for data that is not to be interpreted (not converted when moving data between different systems) by Oracle Database. These datatypes are intended for binary data or byte strings. For example, LONG RAW can be used to store graphics, sound, documents, or arrays of binary data. The interpretation depends on the use.
Oracle Database uses a ROWID datatype to store the address (rowid) of every row in the database.
Physical rowids store the addresses of rows in ordinary tables (excluding index-organized tables), clustered tables, table partitions and subpartitions, indexes, and index partitions and subpartitions.
Logical rowids store the addresses of rows in index-organized tables.
A single datatype called the universal rowid, or UROWID, supports both logical and physical rowids, as well as rowids of foreign tables such as non-Oracle tables accessed through a gateway.
A column of the UROWID datatype can store all kinds of rowids. The value of the COMPATIBLE initialization parameter (for file format compatibility) must be set to 8.1 or higher to use UROWID columns.