Both CHAR and VARCHAR2 types are used to store character string values, however, they behave very differently. The VARCHAR type should not be used:
CHAR
CHAR should be used for storing fix length character strings. String values will be space/blank padded before stored on disk. If this type is used to store variable length strings, it will waste a lot of disk space.
SQL> CREATE TABLE char_test (col1 CHAR(10));
Table created.
SQL> INSERT INTO char_test VALUES ('qwerty');
1 row created.
SQL> SELECT col1, length(col1), dump(col1) "ASCII Dump" FROM char_test;
COL1 LENGTH(COL1) ASCII Dump
---------- ------------ ------------------------------------------------------------
qwerty 10 Typ=96 Len=10: 113,119,101,114,116,121,32,32,32,32
Note: ASCII character 32 is a blank space.
VARCHAR
Currently VARCHAR behaves exactly the same as VARCHAR2. However, this type should not be used as it is reserved for future usage.
SQL> CREATE TABLE varchar_test (col1 VARCHAR2(10));
Table created.
SQL> INSERT INTO varchar_test VALUES ('qwerty');
1 row created.
SQL> SELECT col1, length(col1), dump(col1) "ASCII Dump" FROM varchar_test;
COL1 LENGTH(COL1) ASCII Dump
---------- ------------ ------------------------------------------------------------
qwerty 6 Typ=1 Len=6: 113,119,101,114,116,121
VARCHAR2
VARCHAR2 is used to store variable length character strings. The string value's length will be stored on disk with the value itself.
SQL> CREATE TABLE varchar2_test (col1 VARCHAR2(10));
Table created.
SQL> INSERT INTO varchar2_test VALUES ('qwerty');
1 row created.
SQL> SELECT col1, length(col1), dump(col1) "ASCII Dump" FROM varchar2_test;
COL1 LENGTH(COL1) ASCII Dump
---------- ------------ ------------------------------------------------------------
qwerty 6 Typ=1 Len=6: 113,119,101,114,116,121
