In relational databases – there can be no two identical rows – the columns are arranged in a specific order, which is created when the table is created. The table may not have a single row, but there must be at least one column. – each column has a unique name (within the table), and all values in one column are of the same type (number, text, date.) – at the intersection of each column and row there can be only an atomic value (one value not consisting of a group values).
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.