6 Datatypes

This chapter presents datatypes that are recognized by Oracle and available for use within SQL.

This chapter includes the following sections:

Overview of Datatypes
Oracle Built-In Datatypes
Oracle-Supplied Datatypes
Converting to Oracle Datatypes

Overview of Datatypes

A datatype is a classification of a particular type of information or data. Each value manipulated by Oracle has a datatype. The datatype of a value associates a fixed set of properties with the value. These properties cause Oracle to treat values of one datatype differently from values of another.

The datatypes recognized by Oracle are:

ANSI-supported datatypes

{ CHARACTER [VARYING] (size)
| { CHAR | NCHAR } VARYING (size)
| VARCHAR (size)
| NATIONAL { CHARACTER | CHAR }
     [VARYING] (size)
| { NUMERIC | DECIMAL | DEC }
     [ (precision [, scale ]) ]
| { INTEGER | INT | SMALLINT }
| FLOAT [ (size) ]
| DOUBLE PRECISION
| REAL
}

Oracle built-in datatypes

{ character_datatypes
| number_datatypes
| long_and_raw_datatypes
| datetime_datatypes
| large_object_datatypes
| rowid_datatypes
}

Oracle-supplied datatypes

{ any_types
| XML_types
| spatial_types
| media_types
| expression_filter_type
}

User-defined datatypes

User-defined datatypes use Oracle built-in datatypes and other user-defined datatypes to model the structure and behavior of data in applications

Oracle Built-In Datatypes

This section describes the kinds of Oracle built-in datatypes.

character_datatypes

{ CHAR [ (size [ BYTE | CHAR ]) ]
| VARCHAR2 (size [ BYTE | CHAR ])
| NCHAR [ (size) ]
| NVARCHAR2 (size)
}

datetime_datatypes

{ DATE
| TIMESTAMP [ (fractional_seconds_precision) ]
     [ WITH [ LOCAL ] TIME ZONE ])
| INTERVAL YEAR [ (year_precision) ] TO MONTH
| INTERVAL DAY [ (day_precision) ] TO SECOND
     [ (fractional_seconds_precision) ]
}

large_object_datatypes

{ BLOB | CLOB | NCLOB | BFILE }

long_and_raw_datatypes

{ LONG | LONG RAW | RAW (size) }

number_datatypes

{ NUMBER [ (precision [, scale ]) ]
| BINARY_FLOAT
| BINARY_DOUBLE
}

rowid_datatypes

{ ROWID | UROWID [ (size) ] }

The codes listed for the datatypes are used internally by Oracle Database. The datatype code of a column or object attribute is returned by the DUMP function.

Table 6-1 Built-in Datatype Summary

Code	Datatype	Description
1	`VARCHAR2`(`size` [`BYTE` \| `CHAR`])	Variable-length character string having maximum length `size` bytes or characters. Maximum `size` is 4000 bytes or characters, and minimum is 1 byte or 1 character. You must specify `size` for `VARCHAR2`. `BYTE` indicates that the column will have byte length semantics; `CHAR` indicates that the column will have character semantics.
1	`NVARCHAR2`(`size`)	Variable-length Unicode character string having maximum length `size` characters. The number of bytes can be up to two times `size` for `AL16UTF16` encoding and three times `size` for `UTF8` encoding. Maximum `size` is determined by the national character set definition, with an upper limit of 4000 bytes. You must specify `size` for `NVARCHAR2`.
2	`NUMBER`[(`precision` [, `scale`]])	Number having precision `p` and scale `s`. The precision `p` can range from 1 to 38. The scale `s` can range from -84 to 127.
8	`LONG`	Character data of variable length up to 2 gigabytes, or 2³¹ -1 bytes. Provided for backward compatibility.
12	`DATE`	Valid date range from January 1, 4712 BC to December 31, 9999 AD. The default format is determined explicitly by the `NLS_DATE_FORMAT` parameter or implicitly by the `NLS_TERRITORY` parameter. The size is fixed at 7 bytes. This datatype contains the datetime fields `YEAR`, `MONTH`, `DAY`, `HOUR`, `MINUTE`, and `SECOND`. It does not have fractional seconds or a time zone.
21	`BINARY_FLOAT`	32-bit floating point number. This datatype requires 5 bytes, including the length byte.
22	`BINARY_DOUBLE`	64-bit floating point number. This datatype requires 9 bytes, including the length byte.
180	`TIMESTAMP` [(`fractional_seconds`)]	Year, month, and day values of date, as well as hour, minute, and second values of time, where `fractional_seconds_precision` is the number of digits in the fractional part of the `SECOND` datetime field. Accepted values of `fractional_seconds_precision` are 0 to 9. The default is 6. The default format is determined explicitly by the `NLS_DATE_FORMAT` parameter or implicitly by the `NLS_TERRITORY` parameter. The sizes varies from 7 to 11 bytes, depending on the precision. This datatype contains the datetime fields `YEAR`, `MONTH`, `DAY`, `HOUR`, `MINUTE`, and `SECOND`. It contains fractional seconds but does not have a time zone.
181	`TIMESTAMP` [(`fractional_seconds`)] WITH `TIME` `ZONE`	All values of `TIMESTAMP` as well as time zone displacement value, where `fractional_seconds_precision` is the number of digits in the fractional part of the `SECOND` datetime field. Accepted values are 0 to 9. The default is 6. The default format is determined explicitly by the `NLS_DATE_FORMAT` parameter or implicitly by the `NLS_TERRITORY` parameter. The size is fixed at 13 bytes. This datatype contains the datetime fields `YEAR`, `MONTH`, `DAY`, `HOUR`, `MINUTE`, `SECOND`, `TIMEZONE_HOUR`, and `TIMEZONE_MINUTE`. It has fractional seconds and an explicit time zone.
231	`TIMESTAMP` [(`fractional_seconds`)] WITH `LOCAL` `TIME` `ZONE`	All values of `TIMESTAMP` `WITH` `TIME` `ZONE`, with the following exceptions: Data is normalized to the database time zone when it is stored in the database. When the data is retrieved, users see the data in the session time zone. The default format is determined explicitly by the `NLS_DATE_FORMAT` parameter or implicitly by the `NLS_TERRITORY` parameter. The sizes varies from 7 to 11 bytes, depending on the precision.
182	`INTERVAL` `YEAR` [(`year_precision`)] `TO` `MONTH`	Stores a period of time in years and months, where `year_precision` is the number of digits in the `YEAR` datetime field. Accepted values are 0 to 9. The default is 2. The size is fixed at 5 bytes.
183	`INTERVAL` `DAY` [(`day_precision`)] `TO` `SECOND` [(`fractional_seconds`)]	Stores a period of time in days, hours, minutes, and seconds, where `day_precision` is the maximum number of digits in the `DAY` datetime field. Accepted values are 0 to 9. The default is 2. `fractional_seconds_precision` is the number of digits in the fractional part of the `SECOND` field. Accepted values are 0 to 9. The default is 6. The size is fixed at 11 bytes.
23	`RAW`(`size`)	Raw binary data of length `size` bytes. Maximum `size` is 2000 bytes. You must specify `size` for a `RAW` value.
24	`LONG RAW`	Raw binary data of variable length up to 2 gigabytes.
69	`ROWID`	Base 64 string representing the unique address of a row in its table. This datatype is primarily for values returned by the `ROWID` pseudocolumn.
208	`UROWID` [(`size`)]	Base 64 string representing the logical address of a row of an index-organized table. The optional `size` is the size of a column of type `UROWID`. The maximum size and default is 4000 bytes.
96	`CHAR` [(`size` [`BYTE` \| `CHAR`])]	Fixed-length character data of length `size` bytes. Maximum `size` is 2000 bytes or characters. Default and minimum `size` is 1 byte. `BYTE` and `CHAR` have the same semantics as for `VARCHAR2`.
96	`NCHAR`[(`size`)]	Fixed-length character data of length `size` characters. The number of bytes can be up to two times `size` for `AL16UTF16` encoding and three times `size` for `UTF8` encoding. Maximum `size` is determined by the national character set definition, with an upper limit of 2000 bytes. Default and minimum `size` is 1 character.
112	`CLOB`	A character large object containing single-byte or multibyte characters. Both fixed-width and variable-width character sets are supported, both using the database character set. Maximum size is (4 gigabytes - 1) * (database block size).
112	`NCLOB`	A character large object containing Unicode characters. Both fixed-width and variable-width character sets are supported, both using the database national character set. Maximum size is (4 gigabytes - 1) * (database block size). Stores national character set data.
113	`BLOB`	A binary large object. Maximum size is (4 gigabytes - 1) * (database block size).
114	`BFILE`	Contains a locator to a large binary file stored outside the database. Enables byte stream I/O access to external LOBs residing on the database server. Maximum size is 4 gigabytes.

Oracle-Supplied Datatypes

This section describes the kinds of Oracle-supplied datatypes.

spatial_datatypes

{ SDO_Geometry | SDO_Topo_Geometry |SDO_GeoRaster }

Converting to Oracle Datatypes

SQL statements that create tables and clusters can also use ANSI datatypes and datatypes from the IBM products SQL/DS and DB2. Oracle recognizes the ANSI or IBM datatype name that differs from the Oracle datatype name, records it as the name of the datatype of the column, and then stores the column data in an Oracle datatype based on the conversions shown in the following table.

Table 6-2 ANSI Datatypes Converted to Oracle Datatypes

ANSI SQL Datatype	Oracle Datatype
`CHARACTER(n)` `CHAR(n)`	`CHAR(n)`
`CHARACTER VARYING(n)` `CHAR VARYING(n)`	`VARCHAR(n)`
`NATIONAL CHARACTER(n)` `NATIONAL CHAR(n)` `NCHAR(n)`	`NCHAR(n)`
`NATIONAL CHARACTER VARYING(n)` `NATIONAL CHAR VARYING(n)` `NCHAR VARYING(n)`	`NVARCHAR2(n)`
`NUMERIC(p,s)` `DECIMAL(p,s)` (a)	`NUMBER(p,s)`
`INTEGER` `INT` `SMALLINT`	`NUMBER(38)`
`FLOAT` (b) `DOUBLE PRECISION` (c) `REAL` (d)	`NUMBER`

Notes:

1. The NUMERIC and DECIMAL datatypes can specify only fixed-point numbers. For those datatypes, s defaults to 0.
2. The FLOAT datatype is a floating-point number with a binary precision b. The default precision for this datatypes is 126 binary, or 38 decimal.
3. The DOUBLE PRECISION datatype is a floating-point number with binary precision 126.
4. The REAL datatype is a floating-point number with a binary precision of 63, or 18 decimal.

Table 6-3 SQL/DS and DB2 Datatypes Converted to Oracle Datatypes

SQL/DS or DB2 Datatype	Oracle Datatype
`CHARACTER(n)`	`CHAR(n)`
`VARCHAR(n)`	`VARCHAR(n)`
`LONG VARCHAR(n)`	`LONG`
`DECIMAL(p,s)` (a)	`NUMBER(p,s)`
`INTEGER` `SMALLINT`	`NUMBER(38)`
`FLOAT` (b)	`NUMBER`

Notes:

1. The DECIMAL datatype can specify only fixed-point numbers. For this datatype, s defaults to 0..
2. The FLOAT datatype is a floating-point number with a binary precision b. The default precision for this datatype is 126 binary or 38 decimal.

Do not define columns with the following SQL/DS and DB2 datatypes, because they have no corresponding Oracle datatype:

GRAPHIC
LONG VARGRAPHIC
VARGRAPHIC
TIME

Note that data of type TIME can also be expressed as Oracle datetime data.