Understanding SQL Data Types

SQL data types define the type of value that can be stored in a table column. For example, if you want a column to store only integer values, you can define its data type as INT.

SQL data types can be broadly divided into the following categories:

• Numeric data types such as: INT, TINYINT, BIGINT, FLOAT, REAL, etc.
• Date and Time data types such as: DATE, TIME, DATETIME, etc.
• Character and String data types such as: CHAR, VARCHAR, TEXT, etc.
• Unicode character string data types such as: NCHAR, NVARCHAR, NTEXT, etc.
• Binary data types such as: BINARY, VARBINARY, etc.
• Miscellaneous data types – CLOB, BLOB, XML, CURSOR, TABLE, etc.

In this article, you will learn about different categories of SQL data types.

Relational Database Vendor Differences

Note: Not all data types are supported by every relational database vendor.

For example, the Oracle database doesn’t support DATETIME, and MySQL doesn’t support CLOB. When designing database schemas and writing SQL queries, make sure to check if the data types are supported.

Note: Data types listed here don’t include all the data types. These are the most commonly used data types. Some relational database vendors have their own data types that might not be listed here.

For example, Microsoft SQL Server has MONEY and SMALLMONEY data types, but since they’re not supported by other popular database vendors, they’re not listed here.

Note: Every relational database vendor has its own maximum size limit for different data types.

Be sure to select the appropriate data type for your particular scenario.

SQL Numeric Data Types

Data Type	From	To
BIT	1	0
TINYINT	0	255
SMALLINT	-32,768	32,767
INT	-2,147,483,648	2,147,483,647
BIGINT	-9,223,372,036,854,775,808	9,223,372,036,854,775,807
DECIMAL	-10^38 + 1	10^38 – 1
NUMERIC	-10^38 + 1	10^38 – 1
FLOAT	-1.79E+308	1.79E+308
REAL	-3.40E+38	3.40E+38

SQL Date and Time Data Types

Data Type	Description
DATE	Stores date in the format YYYY-MM-DD
TIME	Stores time in the format HH:MI:SS
DATETIME	Stores date and time information in the format YYYY-MM-DD HH:MI:SS
TIMESTAMP	Stores number of seconds passed since the Unix epoch (‘1970-01-01 00:00:00’ UTC)
YEAR	Stores year in a 2-digit or 4-digit format. Range 1901 to 2155 in 4-digit format. Range 70 to 69, representing 1970 to 2069.

SQL Character and String Data Types

Data Type	Description
CHAR	Fixed length with a maximum length of 8,000 characters
VARCHAR	Variable-length storage with a maximum length of 8,000 characters
VARCHAR(max)	Variable-length storage with provided max characters, not supported in MySQL
TEXT	Variable-length storage with a maximum size of 2GB data

Note: These data types are for character streams. They should not be used with Unicode data.

SQL Unicode Character and String Data Types

Data Type	Description
NCHAR	Fixed length with a maximum length of 4,000 characters
NVARCHAR	Variable-length storage with a maximum length of 4,000 characters
NVARCHAR(max)	Variable-length storage with provided max characters
NTEXT	Variable-length storage with a maximum size of 1GB data

Note: These data types are not supported in MySQL databases.

SQL Binary Data Types

Data Type	Description
BINARY	Fixed length with a maximum length of 8,000 bytes
VARBINARY	Variable-length storage with a maximum length of 8,000 bytes
VARBINARY(max)	Variable-length storage with provided max bytes
IMAGE	Variable-length storage with a maximum size of 2 GB binary data

SQL Miscellaneous Data Types

Data Type	Description
CLOB	Character large objects that can hold up to 2 GB
BLOB	For large binary objects
XML	For storing XML data
JSON	For storing JSON data

Conclusion

In this article, you learned about different categories of SQL data types. Understanding SQL Data Types