Varchar

Varchar, often written as VARCHAR or VARCHAR2 (in Oracle), is a data type in many database management systems (DBMS). It is short for "variable character" and is used to store character strings of varying lengths. The defining characteristic of varchar is that it does not pre-allocate a fixed amount of space for each stored value; instead, it only uses the amount of space required to store the actual characters, plus a small overhead for length information.

A varchar column is typically defined with a maximum length, such as VARCHAR(255). This specifies the maximum number of characters that can be stored in that column. When a value is stored, the database only allocates the space needed for that value, up to the specified maximum. If a value exceeds the maximum length, it is usually truncated (depending on the DBMS settings) or rejected, resulting in an error.

The use of varchar is advantageous in situations where the length of the strings being stored varies significantly, as it saves storage space compared to fixed-length character data types like CHAR. This is particularly beneficial when dealing with large datasets where space optimization is crucial.

The specific implementation of varchar can differ between database systems. Some databases may treat trailing spaces differently, either trimming them automatically or preserving them as part of the string. The maximum length allowed for a varchar column also varies depending on the database system used.