Задача про бинарное дерево
#почитать
Пару слов о необходимом арсенале. Для решения задачи, понадобится следующее:
▫️Изучить, либо освежить, как используются, в SQL, условные конструкции CASE WHEN THEN;
▫️Повторить использование IN в связке с вложенным запросом, а именно, перед ним.
▫️Вспомнить, что делает оператор DISTINCT;
Ну и не забывать, что когда проверяем значение на NULL, то пишем не '=', '<>', '!=' а IS NULL / IS NOT NULL.
BY SQL для тестировщика
In general, many financial experts support their clients’ desire to buy cryptocurrency, but they don’t recommend it unless clients express interest. “The biggest concern for us is if someone wants to invest in crypto and the investment they choose doesn’t do well, and then all of a sudden they can’t send their kids to college,” says Ian Harvey, a certified financial planner (CFP) in New York City. “Then it wasn’t worth the risk.” The speculative nature of cryptocurrency leads some planners to recommend it for clients’ “side” investments. “Some call it a Vegas account,” says Scott Hammel, a CFP in Dallas. “Let’s keep this away from our real long-term perspective, make sure it doesn’t become too large a portion of your portfolio.” In a very real sense, Bitcoin is like a single stock, and advisors wouldn’t recommend putting a sizable part of your portfolio into any one company. At most, planners suggest putting no more than 1% to 10% into Bitcoin if you’re passionate about it. “If it was one stock, you would never allocate any significant portion of your portfolio to it,” Hammel says.
Launched in 2013, Telegram allows users to broadcast messages to a following via “channels”, or create public and private groups that are simple for others to access. Users can also send and receive large data files, including text and zip files, directly via the app.The platform said it has more than 500m active users, and topped 1bn downloads in August, according to data from SensorTower.SQL для тестировщика from us