2
Selecting a Datatype
This chapter discusses how to use Oracle built-in datatypes in applications. Topics include:
■Summary of Oracle Built-In Datatypes
■Representing Character Data
■Representing Numeric Data with Number and Floating-Point Datatypes
■Representing Date and Time Data
■Representing Conditional Expressions as Data
■Representing Geographic Coordinate Data
■Representing Image, Audio, and Video Data
■Representing Searchable Text Data
■Representing Large Amounts of Data
■Addressing Rows Directly with the ROWID Datatype
■ANSI/ISO, DB2, and SQL/DS Datatypes
■How Oracle Database Converts Datatypes
■Representing Dynamically Typed Data
■Representing XML Data
Selecting a Datatype 2-1
Summary of Oracle Built-In Datatypes
See Also:
■
■
■
Oracle Database Application Developer's Guide - Object-Relational Features for information about more complex types, such as object types, varrays, and nested tables
Oracle Database Application Developer's Guide - Large Objects for information about LOB datatypes
PL/SQL User's Guide and Reference for information about the PL/SQL datatypes. Many SQL datatypes are the same or similar in PL/SQL.
Summary of Oracle Built-In Datatypes
A datatype associates a fixed set of properties with the values that can be used in a column of a table or in an argument of a procedure or function. These properties cause Oracle Database to treat values of one datatype differently from values of another datatype. For example, Oracle Database can add values of NUMBER datatype, but not values of RAW datatype.
Oracle supplies the following built-in datatypes:
■Character datatypes
– CHAR
■
■
–NCHAR
– VARCHAR2 and VARCHAR (synonymous with VARCHAR2)
–NVARCHAR2
–CLOB
–NCLOB
–LONG
Numerical datatypes:
–BINARY_FLOAT
–BINARY_DOUBLE
–NUMBER
Time and date datatypes:
–DATE
–INTERVAL DAY TO SECOND
2-2 Oracle Database Application Developer's Guide - Fundamentals
Summary of Oracle Built-In Datatypes
–INTERVAL YEAR TO MONTH
–TIMESTAMP
–TIMESTAMP WITH TIME ZONE
–TIMESTAMP WITH LOCAL TIME ZONE
■Binary datatypes
–BLOB
–BFILE
–RAW
–LONG RAW
■Row address datatypes
–ROWID
–UROWID
See Also:
■Oracle Database SQL Reference for general descriptions of these datatypes
■Oracle Database Application Developer's Guide - Large Objects for information about the LOB datatypes
Table 2–1 summarizes the information about each Oracle built-in datatype.
Selecting a Datatype 2-3
Summary of Oracle Built-In Datatypes
Table 2–1 Summary of Oracle Built-In Datatypes
|
|
Column Length / Default |
Datatype |
Description |
Values |
CHAR |
Fixed-length character data |
[(size [BYTE | CHAR])] |
of length size bytes or |
|
characters. |
Fixed for every row in the table (with trailing blanks); maximum size is 2000 bytes per row, default size is 1 byte per row. When neither BYTE nor CHAR is specified, the setting of NLS_LENGTH_ SEMANTICS at the time of column creation determines which is used. Consider the character set (single-byte or multibyte) before setting size.
VARCHAR2
(size [BYTE | CHAR])
Variable-length character data, with maximum length size bytes or characters. BYTE or CHAR indicates that the column has byte or character semantics, respectively. A size must be specified.
Variable for each row, up to 4000 bytes per row. When neither BYTE nor CHAR is specified, the setting of NLS_LENGTH_ SEMANTICS at the time of column creation determines which is used. Consider the character set (single-byte or multibyte) before setting size.
NCHAR [(size)] |
Fixed-length Unicode |
|
character data of length |
|
size characters. The |
|
number of bytes is twice this |
|
number for the AL16UTF16 |
|
encoding and 3 times this |
|
number for the UTF8 |
|
encoding.) |
Fixed for every row in the table (with trailing blanks). The upper limit is 2000 bytes per row. Default size is 1 character.
NVARCHAR2 (size) |
Variable-length Unicode |
|
character data of maximum |
|
length size characters. The |
|
number of bytes may be up |
|
to 2 times size for a the |
|
AL16UTF16 encoding and 3 |
|
times this number for the |
|
UTF8 encoding. A size |
|
must be specified. |
Variable for each row. The upper limit is 4000 bytes per row.
2-4 Oracle Database Application Developer's Guide - Fundamentals
Summary of Oracle Built-In Datatypes
Table 2–1 (Cont.) Summary of Oracle Built-In Datatypes
Datatype
CLOB
NCLOB
LONG
|
Column Length / Default |
Description |
Values |
Single-byte or multibyte character data. Both fixed-width and variable-width character sets are supported, and both use the CHAR character set.
Unicode national character set (NCHAR) data. Both fixed-width and variable-width character sets are supported, and both use the NCHAR character set.
Variable-length character data. Provided for backward compatibility.
Up to 232 - 1 bytes * (database block size), or 4
gigabytes * block size.1 See
Oracle Database Application Developer's Guide - Large Objects.
Up to 232 - 1 bytes * (database block size), or 4
gigabytes * block size. 1
See Oracle Database Application Developer's Guide - Large Objects.
Variable for each row in the table, up to 231 - 1 bytes, or 2 gigabytes, per row.
BINARY_FLOAT |
32-bit floating-point |
|
number. |
BINARY_DOUBLE |
64-bit floating-point |
|
number. |
NUMBER |
Variable-length numeric |
[(prec | prec, scale)] |
data. Precision prec is the |
|
the total number of digits; |
|
scale scale is the number |
|
of digits to the right of the |
|
decimal point. Precision can |
|
range from 1 to 38. Scale |
|
can range from -84 to 127. |
|
With precision specified, |
|
this is a floating-point |
|
number; with no precision |
|
specified, it is a fixed-point |
|
number. |
4 bytes.
8 bytes.
Variable for each row. The maximum space available for a given column is 21 bytes per row.
Selecting a Datatype 2-5
Summary of Oracle Built-In Datatypes
Table 2–1 |
(Cont.) Summary of Oracle Built-In Datatypes |
|
|
|
|
|
|
Column Length / Default |
Datatype |
Description |
Values |
DATE |
Fixed-length date and time |
|
data, ranging from Jan. 1, |
|
4712 B.C.E. to Dec. 31, 9999 |
|
C.E. |
Fixed at 7 bytes for each row in the table. Default format is a string (such as DD-MON-RR) specified by the NLS_DATE_FORMAT parameter.
INTERVAL YEAR [(yr_prec)] TO MONTH
A period of time, |
Fixed at 5 bytes. |
represented as years and |
|
months. The yr_prec is |
|
the number of digits in the |
|
YEAR field of the date. The |
|
precision can be from 0 to 9, |
|
and defaults to 2 digits. |
|
INTERVAL DAY [(day_prec)] TO SECOND [(frac_sec_prec)]
TIMESTAMP [(frac_sec_prec)]
A period of time, represented as days, hours, minutes, and seconds. The day_prec and frac_sec_ prec are the number of digits in the DAY and the fractional SECOND fields of the date, respectively. These precision values can each be from 0 to 9, and they default to 2 digits for day_ prec and 6 digits for frac_sec_prec.
A value representing a date and time, including fractional seconds. (The exact resolution depends on the operating system clock.)
The frac_sec_prec specifies the number of digits in the fractional second part of the SECOND date field. The frac_sec_ prec can be from 0 to 9, and defaults to 6 digits.
Fixed at 11 bytes.
Varies from 7 to 11 bytes, depending on the precision. The default is determined by the NLS_ TIMESTAMP_FORMAT initialization parameter.
2-6 Oracle Database Application Developer's Guide - Fundamentals
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|
|
Summary of Oracle Built-In Datatypes |
|
|
|
|
|
Table 2–1 |
(Cont.) Summary of Oracle Built-In Datatypes |
|
|
|
|
|
|
|
|
Column Length / Default |
|
Datatype |
Description |
Values |
TIMESTAMP [(frac_sec_prec)] WITH TIME ZONE
TIMESTAMP [(frac_sec_prec)] WITH LOCAL TIME ZONE
BLOB
BFILE
A value representing a date and time, plus an associated time zone setting. The time zone can be an offset from UTC, such as '-5:0', or a region name, such as
'US/Pacific'.
The frac_sec_prec is as for datatype TIMESTAMP.
Similar to TIMESTAMP WITH TIME ZONE, except that the data is normalized to the database time zone when stored, and adjusted to match the client's time zone when retrieved.
The frac_sec_prec is as for datatype TIMESTAMP.
Unstructured binary data.
Address of a binary file stored outside the database. Enables byte-stream I/O access to external LOBs residing on the database server.
Fixed at 13 bytes. The default is determined by the NLS_TIMESTAMP_ TZ_FORMAT initialization parameter.
Varies from 7 to 11 bytes, depending on frac_ sec_prec. The default is determined by the NLS_ TIMESTAMP_FORMAT initialization parameter.
Up to 232 - 1 bytes * (database block size), or 4
gigabytes * block size.1 See
Oracle Database Application Developer's Guide - Large Objects.
The referenced file can be up to 232 - 1 bytes * (database block size), or 4
gigabytes * block size.1 See
Oracle Database Application Developer's Guide - Large Objects.
RAW (size) |
Variable-length raw binary |
|
data. A size, which is the |
|
maximum number of bytes, |
|
must be specified. Provided |
|
for backward compatibility. |
Variable for each row in the table, up to 2000 bytes per row.
Selecting a Datatype 2-7