Что такое "нормальная форма" БД и какие формы существуют.
▫️Что такое нормализация
▫️Что такое избыточность данных - примеры
▫️Какие бывают нормальные формы БД
▫️Ненормализованная форма
▫️Пример нормальной формы
▫️Еще пример
▫️Что такое декомпозиция
▫️Нормальная форма Бойса-Кодда
▫️Четвертая нормальная форма
▫️Почему обычно не нормализуют до 5 или 6 формы
▫️Пятая и шестая нормальная формы
BY SQL для тестировщика
The SSE was the first modern stock exchange to open in China, with trading commencing in 1990. It has now grown to become the largest stock exchange in Asia and the third-largest in the world by market capitalization, which stood at RMB 50.6 trillion (US$7.8 trillion) as of September 2021. Stocks (both A-shares and B-shares), bonds, funds, and derivatives are traded on the exchange. The SEE has two trading boards, the Main Board and the Science and Technology Innovation Board, the latter more commonly known as the STAR Market. The Main Board mainly hosts large, well-established Chinese companies and lists both A-shares and B-shares.
Some messages aren’t supposed to last forever. There are some Telegram groups and conversations where it’s best if messages are automatically deleted in a day or a week. Here’s how to auto-delete messages in any Telegram chat. You can enable the auto-delete feature on a per-chat basis. It works for both one-on-one conversations and group chats. Previously, you needed to use the Secret Chat feature to automatically delete messages after a set time. At the time of writing, you can choose to automatically delete messages after a day or a week. Telegram starts the timer once they are sent, not after they are read. This won’t affect the messages that were sent before enabling the feature.
SQL для тестировщика from no