How to select left and right substrings in SQL Server

Do you need to select part of a substring in SQL Server's Transact SQL? There are three useful functions for doing this - Left, Right and Substring.

The Transact SQL Left and Right functions are used to truncate strings after a specified number of characters from either the left side or the right side of the string, respectively.

Both the Left and Right functions need two arguments to be supplied - the string to be truncated, and the length of the string that should be retained.

To show an example of the Left function, the SQL statement below will return "sq":

SELECT Left('sql server', 2)

The example below uses the Left function to create a four character DataCode column from the first four characters of the DataDescription column of the FinancialData database table:

SELECT DataID, DataDescription, Left(DataDescription, 4) AS DataCode FROM FinancialData ORDER BY DataID

By contrast, the Right Transact SQL function truncates a string from the right side of that string. This example creates a DataCode column that is based on the final three characters of the DataDescription column:

SELECT DataID, DataDescription, Right(DataDescription, 3) AS DataCode FROM FinancialData ORDER BY DataID

To return part of a string, use the Substring function.