Chapter 2: Transact-SQL Functions

lower

Returns the lowercase equivalent of the specified expression.

lower(char_expr | uchar_expr)

char_expr: is a character-type column name, variable, or constant expression of char, varchar, nchar, or nvarchar type.

uchar_expr: is a character-type column name, variable, or constant expression of unichar or univarchar type.

select lower(city) from publishers

-------------------- 
boston               
washington           
berkeley

lower, a string function, converts uppercase to lowercase, returning a character value.
lower is the inverse of upper.
If char_expr or uchar_expr is NULL, returns NULL.
For general information about string functions, see “String functions”.

ANSI SQL – Compliance level: Transact-SQL extension.

Any user can execute lower.