RE: Data Types

Concepts manual  

VARCHAR2 and VARCHAR Datatypes

BM_707The VARCHAR2 datatype stores variable-length character strings. When you create a table with a VARCHAR2 column, you specify a maximum string length (in bytes, not characters) between 1 and 4000 for the VARCHAR2 column. For each row, Oracle stores each value in the column as a variable-length field unless a value exceeds the column's maximum length, in which case Oracle returns an error.

BM_3417For example, assume you declare a column VARCHAR2 with a maximum size of 50 characters. In a single-byte character set, if only 10 characters are given for the VARCHAR2 column value in a particular row, the column in the row's row piece stores only the 10 characters (10 bytes), not 50.

VARCHAR Datatype

The VARCHAR datatype is currently synonymous with the VARCHAR2 datatype. However, in a future version of Oracle, VARCHAR might store variable-length character strings compared with different comparison semantics. Therefore, to avoid possible changes in behavior you should always use the VARCHAR2 datatype to store variable-length character strings.

NCHAR and NVARCHAR2 Datatype

The NCHAR and NVARCHAR2 datatypes store NLS character data. The NCHAR datatype stores fixed-length character strings that correspond to a fixed-length or variable-length national character set. The NVARCHAR2 datatype stores variable-length character strings.

When you create a table with an NCHAR or NVARCHAR2 column, you specify a maximum size that is either the number of characters (for a fixed-length national character set) or the number of bytes (for a variable-length national character set).

• BM_4243The maximum length for an NCHAR column is 2000 bytes, or the number of characters that can be stored in 2000 bytes.
• BM_4242The maximum length for an NVARCHAR2 column is 4000 bytes, or the number of characters that can be stored in 4000 bytes.
• -----Original Message----- Sent: 21 June 2002 07:23 To: Multiple recipients of list ORACLE-L

i wanted to know the exact difference between the following data types ->  

NCHAR
NVARCHAR2
VARCHAR2
VARCHAR Thanks and regards,

Santosh  

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