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 specifysize for VARCHAR2.

BYTE indicates that the column will have byte length semantics. CHAR indicates that the column will have character semantics.

VARCHAR2(4000 BYTE)可以存4000个字母，2000个汉字

VARCHAR2(4000 CHAR)可以存4000个字母，4000个汉字

1

NVARCHAR2(size)

Variable-length Unicode character string having maximum length sizecharacters. The number of bytes can be up to two times size for AL16UTF16encoding and three times size for UTF8encoding. Maximum size is 2000 bytes. You must specify size for NVARCHAR2.

2

NUMBER [ (p [, s]) ]

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. Both precision and scale are in decimal digits. A NUMBER value requires from 1 to 22 bytes.

2

FLOAT [(p)]

A subtype of the NUMBER data type having precision p. A FLOAT value is represented internally as NUMBER. The precision p can range from 1 to 126 binary digits. A FLOAT value requires from 1 to 22 bytes.To convert from binary to decimal precision, multiply n by0.30103. To convert from decimal to binary precision, multiply the decimal precision by 3.32193.

8

LONG

Character data of variable length up to 2 gigabytes, or 2³¹ -1 bytes. Provided for backward compatibility.

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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_TERRITORYparameter. The size is fixed at 7 bytes.This data type contains the datetime fields YEAR, MONTH, DAY, HOUR, MINUTE, and SECOND. It does not have fractional seconds or a time zone.

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BINARY_FLOAT

32-bit floating point number. This data type requires 4 bytes.

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BINARY_DOUBLE

64-bit floating point number. This data type requires 8 bytes.

180

TIMESTAMP[(fractional_seconds_precision)]

Year, month, and day values of date, as well as hour, minute, and second values of time, wherefractional_seconds_precision is the number of digits in the fractional part of the SECOND datetime field. Accepted values offractional_seconds_precision are 0 to 9. The default is 6. The default format is determined explicitly by theNLS_TIMESTAMP_FORMAT parameter or implicitly by the NLS_TERRITORYparameter. The size is 7 or 11 bytes, depending on the precision. This data type 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, wherefractional_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_TIMESTAMP_FORMAT parameter or implicitly by the NLS_TERRITORYparameter. The size is fixed at 13 bytes. This data type contains the datetime fields YEAR, MONTH, DAY, HOUR, MINUTE,SECOND, TIMEZONE_HOUR, andTIMEZONE_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_TIMESTAMP_FORMATparameter or implicitly by theNLS_TERRITORY parameter. The size is 7 or 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)] TOSECOND [(fractional_seconds)]

Stores a period of time in days, hours, minutes, and seconds, where

• day_precision is the maximum number of digits in the DAYdatetime field. Accepted values are 0 to 9. The default is 2.

• fractional_seconds_precisionis 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.

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LONG RAW

Raw binary data of variable length up to 2 gigabytes.

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ROWID

Base 64 string representing the unique address of a row in its table. This data type is primarily for values returned by the ROWID pseudocolumn.

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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.

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CHAR [(size [BYTE | CHAR])]

Fixed-length character data of lengthsize bytes or characters. Maximumsize is 2000 bytes. Default and minimum size is 1 byte.

BYTE and CHAR have the same semantics as for VARCHAR2.

CHAR(2000 BYTE)可以存2000个字母，1000个汉字

CHAR(2000 CHAR)可以存2000个字母，2000个汉字

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NCHAR[(size)]

Fixed-length character data of lengthsize characters. The number of bytes can be up to two times size forAL16UTF16 encoding and three timessize for UTF8encoding. Maximum size is 1000 bytes. Default and minimum size is 1 character.

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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).

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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.

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BLOB

A binary large object. Maximum size is (4 gigabytes - 1) * (database block size).

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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.The locator maintains the directory name and the filename.