Field Type of 0racle

Field Type	Description	Field Length and default value
Char (Size)	It is used to save string data of a fixed length (size) byte.	The fixed length of each line (space filling for the remaining part). The maximum length is 2000 bytes for each line, and the default value is 1 byte for each line. Before setting the length (size), consider the character set as single-byte or multi-byte.
Varchar2 (Size)	Used to save variable-length string data. The maximum byte length is specified by (size.	The length of each line is variable. The maximum length is 4000 bytes. Before setting the length (size), consider the character set as single-byte or multi-byte.
Nchar (Size)	Determined by the character set, the characters or bytes of a fixed length (size) are saved.	The fixed length of each line (the remaining part is filled with spaces ). For character sets with a fixed width, the length (size) refers to the number of characters. For character sets with a wider width, the length (size) refers to the number of bytes. The maximum length (size) depends on the length of the byte stored in one character. The maximum length of each line is 2000 bytes. It is determined by the character set that the default value is 1 character or 1 byte.
Nvarchar2 (Size)	The character set determines whether to save Long characters or bytes. The maximum length is specified by (size.	Each line gets longer. For character sets with a fixed width, the length (size) refers to the number of characters. For character sets with a wider width, the length (size) refers to the number of bytes. The maximum length (size) depends on the length of the byte stored in one character. The maximum length of each line is 4000 bytes. It is determined by the character set that the default value is 1 character or 1 byte.
Long	Saves variable-length string data.	The length of each row in the table can be variable. The maximum length is 231-1 bytes or 2 GB for each row.
Integer	Save a small integer. It can also write int in brief.	See the definition in SYS. Standard: Subtype integer is number (38,0 ); Subtype Int Is integer; Subtype smallint is number (38,0 ); Subtype decimal is number (38,0 ); Subtype numeric is decimal; Subtype DEC is decimal;
Decimal (P, S)	P is the integer, and s is the decimal place.	The precision is higher than the number.
Float	Floating Point Type	Number (38), Double Precision
Real	Real Number Type	Number (63), higher accuracy
Number (P, S)	Save variable-length numbers. The maximum value of precision is P, and the maximum value of/or valid digit number S is 38.	Each line gets longer. The maximum length of each line is 21 bytes.
Date	The data of a specified date or time is stored in the range of 4712/01/01 BC to 9999/12/31 a.m.	Each line is fixed to a 7-byte length, and the default value of the date description, such as the DD-MON-YY, is set by the nls_date_format parameter.
Raw (Size)	Stores variable-length binary data. The maximum length is specified by size.	The length of each row in the table can be variable. The maximum length is 2000 bytes per row.
Long raw	Stores variable-length binary data.	The length of each row in the table can be variable. The maximum length is 231-1 bytes or 2 GB for each row.
Blob	Stores binary data.	The maximum length is 232-1 bytes or 4 GB.
Clob	Stores single-byte character data.	The maximum length is 232-1 bytes or 4 GB.
Nclob	Saves the character data of a single byte specified by the character set, fixed-width multibyte, or extended multibyte.	The maximum length is 232-1 bytes or 4 GB.
Bfile	Binary data stored in an external file.	The maximum length is 232-1 bytes or 4 GB.

This table is being updated. You are welcome to correct and add it.