The LOWER string function returns a character expression after converting uppercase character data to lowercase. The syntax of the LOWER string function is as follows:
LOWER ( < character_expression > )
The < character_expression > is an expression of character or binary data. < character_expression > can be a constant, variable or column and it must be of a data type that is implicitly convertible to VARCHAR; otherwise, the CAST function needs to explicitly convert < character_expression >.
Here are sample uses of the LOWER string function
Usage #1 : Determine if All Characters in a String are in Lower Case
DECLARE @Input VARCHAR(20) = 'sql server helper'
SELECT CASE WHEN LOWER(@Input) = @Input COLLATE Latin1_General_BIN
THEN 'Yes'
ELSE 'No' END AS [IsAllLowerCase]
IsAllLowerCase
---------------
Yes
Usage #2 : Determine if a Character is a Letter of the Alphabet
DECLARE @Input1 CHAR(1)
DECLARE @Input2 CHAR(1)
SET @Input1 = '1'
SET @Input2 = 'A'
SELECT CASE WHEN ASCII(LOWER(@Input1)) != ASCII(UPPER(@Input1))
THEN 'Yes'
ELSE 'No' END AS [IsAlphabet1],
CASE WHEN ASCII(LOWER(@Input2)) != ASCII(UPPER(@Input2))
THEN 'Yes'
ELSE 'No' END AS [IsAlphabet2]
IsAlphabet1 IsAlphabet2
------------ ------------
No Yes