This function is used to convert , value of column in lowercase . If value of column already in a lowercase then it doesn't covert . It convert only if value of filed is in uppercase .
Syntax :

select lcase ( column_name ) from table_name ;

Syntax for SQL :

select lower ( column_name ) from table_name ;

Example :
Table name : Employee_Info

  Id        Employee_name          Employee_Age               Employee _Salary
  1            Mukesh                  23                           100000
  2            Ayush                   24                           200000
  3            Ishan                   20                           400000
  4            Pranav                  35                           700000
  5            Abhishek                26                           800000
  6            Ravi                    25                           300000
  7            David                   40                           800000

Query to convert column value in lowercase .

select lcase ( Employee_name ) from Employee_Info ;

Output :

 Employee_name
  mukesh
  ayush
  ishan
  pranav
  abhishek
  ravi
  david