Storing Character Data

The VARCHAR2 datatype stores variable-length character literals.

When creating a VARCHAR2 column in a table, you must specify a string length between 1 and 4000 bytes for the VARCHAR2 column. Set the size to the maximum number of characters to be stored in the column. For example, a column to hold the last name of employees can be restricted to 25 bytes by defining it as VARCHAR2(25).

For each row, Oracle Database XE 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. Using VARCHAR2 saves on space used by the table. For most cases where you need to store character data, you would use the VARCHAR2 datatype.

The CHAR datatype stores fixed-length character literals.

When creating a CHAR column in a table, you must specify a string length between 1 and 2000 bytes for the CHAR column. For each row, Oracle Database XE stores each value in the column as a fixed-length field. If the value of the character data is less than specified length of the column, then the value is blank-padded to the fixed length. If a value is too large, Oracle Database XE returns an error.

NCHAR and NVARCHAR2 datatypes store only Unicode character data.

The NVARCHAR2 datatype stores variable-length Unicode character literals. The NCHAR datatype stores fixed-length Unicode character literals. See Working in a Global Environment for information about using Unicode data and globalization support.

Space usage

To store data more efficiently, use the VARCHAR2 datatype. The CHAR datatype adds blanks to maintain a fixed column length for all column values, whereas the VARCHAR2 datatype does not add extra blanks.

Comparison semantics

Use the CHAR datatype when trailing blanks are not important in string comparisons. Use the VARCHAR2 datatype when trailing blanks are important in string comparisons.

Future compatibility

The CHAR and VARCHAR2 datatypes are fully supported.