What is the difference between CHAR and VARCHAR data types in SQL?

CHAR is a fixed-length data type, while VARCHAR is a variable-length data type in SQL.

In SQL, CHAR and VARCHAR are both used to store string type data in the database. However, they handle the storage and retrieval of this data differently. CHAR is a fixed-length data type, meaning that it will always use the same amount of storage space for each entry, regardless of the actual length of the data. For example, if you define a CHAR(10) column, it will always use 10 characters of storage, even if you only store a 2-character string. Any unused space is filled with blank spaces.

On the other hand, VARCHAR is a variable-length data type. It only uses as much storage space as the actual data requires, plus some additional space to record the length of the data. For example, if you define a VARCHAR(10) column and store a 2-character string, it will only use 2 characters of storage (plus a little extra), not 10. This can make VARCHAR more space-efficient than CHAR, especially when storing shorter strings.

However, this flexibility comes with a cost. Because VARCHAR has to keep track of the length of each value, it can be slower to retrieve data from a VARCHAR column than from a CHAR column. This is especially true when the database has to sort or compare VARCHAR values, as it has to take into account the variable lengths.

In summary, the main difference between CHAR and VARCHAR data types in SQL is how they handle storage and retrieval of data. CHAR is a fixed-length data type that always uses the same amount of storage space, while VARCHAR is a variable-length data type that only uses as much storage as the actual data requires. This makes VARCHAR more space-efficient, but potentially slower to retrieve data from, especially when sorting or comparing values.