Two common ways of formatting table/column names are
SELECT FirstName, LastName FROM Employees WHERE Salary > 500;
SELECT first_name, last_name FROM employees WHERE salary > 500;
Names should describe what is stored in their object. This implies that column names usually should be singular. Whether table names should use singular or plural is a heavily discussed question, but in practice, it is more common to use plural table names.
Adding prefixes or suffixes like
col reduces readability, so avoid them.
However, they are sometimes used to avoid conflicts with SQL keywords, and often used with triggers and indexes (whose names are usually not mentioned in queries).
SQL keywords are not case sensitive. However, it is common practice to write them in upper case.