Data is the driving force behind most computer systems and databases. Developers and database administrators utilize different data types to store various kinds of data. Popular data types include text, integers, floating-points and dates.
Two common data types found in SQL (Structured Query Language) are CHAR and VARCHAR.
Although they may seem similar, they have fundamental differences, and knowing how to use them correctly can help improve the performance of your SQL database.
In this article, we’ll explore the differences between CHAR and VARCHAR data types, how they work and when to use them in your database.
What is CHAR?
The CHAR data type is a fixed-length string data type that stores a sequence of characters with a specific length in bytes. The length of the string is set when the column is created and cannot be altered.
For example, if we create a column with CHAR(10), then the column will always have 10 characters. If we insert a value of less than 10 characters, the remaining space will be filled with empty spaces. If the value is more than 10 characters, the extra characters will be truncated.
Here’s an example:
CREATE TABLE users (
In this example, we created a table named users with two columns 'id' and 'name'.
The column name is defined as CHAR(10), which means it can only store characters with a length of 10, and it will always allocate 10 bytes of space.
If we insert a name “John”, the value will be stored as “John ”, with six empty spaces added at the end.
The space allocation is done to make all the values in the column occupy the same amount of disk space.
CHAR is useful for storing fixed-length data such as postal codes, phone numbers, and account numbers. It is also more efficient on storage than VARCHAR.
What is VARCHAR?
The VARCHAR data type is a variable-length string data type that stores a sequence of characters with a specific length in bytes, where the length can be altered.
For example, if we create a column with VARCHAR(10), then the column can store between 1 to 10 characters, and if we insert a value of less than 10 characters, the remaining space will remain free.
Here’s an example:
CREATE TABLE users (
In this example, we also have a table named 'users' with two columns 'id' and 'name', but in contrast, the 'name' column is defined as VARCHAR(10).
If we insert a name “John” into this table, then the value will be stored as “John”, and we won't have any extra spaces added.
VARCHAR is suitable for storing variable-length data such as names, addresses, and emails, where the length of the value can vary.
What are the differences?
The main difference between CHAR and VARCHAR is how they store their data. As previously stated, CHAR values are always stored as fixed-length values and take up the same amount of space for each value, while VARCHAR values are only allocated the necessary amount of storage in bytes.
CHAR values use trailing spaces, while VARCHAR does not. This means that CHAR values may take up more space than VARCHAR values.
One of the advantages of using CHAR is that it is faster when searching through the database using the WHERE clause.
When to use CHAR and when to use VARCHAR?
Since both CHAR and VARCHAR are used to store string data types, the choice of which one to use depends on the data being stored.
Here are a few scenarios to consider:
1. If the data being stored is fixed-length, use CHAR.
2. If the data being stored is of varying length, use VARCHAR.
3. If specific storage size is needed, use CHAR.
4. If space optimization is a priority, use VARCHAR.
5. If you are unsure, use VARCHAR.
In conclusion, CHAR and VARCHAR are two important data types in SQL, and each has its strengths and weaknesses. The choice of which one to use depends on the type of data that will be stored, and using the right one is essential for efficient storage and querying of data.
CHAR is a fixed-length string data type suitable for storing data that is always consistent in length, while VARCHAR is a variable-length string data type suitable for storing data whose length may vary.
Understanding how these data types work and when to use them properly will help you optimize storage and querying performance in your database.