These functions return 1 if their first argument is less than (lt),
    less than or equivalent (lte), greater than (gt), greater than or
    equivalent (gte), equivalent (equ), or not equivalent (neq) to the
    second argument, respectively. If the arguments are not of the same type,
    then an appropriate type coercion is done for them before
    comparison. These functions correspond to SQL query operators <, <=, >,
    >=, = and <> and are needed because the SQL syntax does not
    allow these operators to be used on the left side of
    FROM keyword in a SELECT
    statement.