🎯 Цель: Найти количество уникальных пользователей, если: - Регистр не учитывается (`alice` = `ALICE`) - Пробелы игнорируются - Для @gmail.com: — Убираются точки в имени — Всё после + отрезается
✅ SQL-решение:
SELECT COUNT(DISTINCT normalized_email) AS unique_users FROM ( SELECT CASE WHEN email ILIKE '%@gmail.com' THEN REGEXP_REPLACE( SPLIT_PART(SPLIT_PART(LOWER(TRIM(email)), '+', 1), '@', 1), '\.', '', 'g' ) || '@gmail.com' ELSE LOWER(REPLACE(TRIM(email), ' ', '')) END AS normalized_email FROM users ) AS cleaned;
🔍 Как это работает:
LOWER(TRIM(email)) — убираем пробелы и регистр
SPLIT_PART(..., '+', 1) — отрезаем всё после +
REGEXP_REPLACE(..., '\.', '', 'g') — удаляем точки
Считаем DISTINCT, чтобы получить число уникальных email'ов
🔥 Используй такие трюки для: • антифрода • чистки базы • аналитики поведения пользователей
🎯 Цель: Найти количество уникальных пользователей, если: - Регистр не учитывается (`alice` = `ALICE`) - Пробелы игнорируются - Для @gmail.com: — Убираются точки в имени — Всё после + отрезается
✅ SQL-решение:
SELECT COUNT(DISTINCT normalized_email) AS unique_users FROM ( SELECT CASE WHEN email ILIKE '%@gmail.com' THEN REGEXP_REPLACE( SPLIT_PART(SPLIT_PART(LOWER(TRIM(email)), '+', 1), '@', 1), '\.', '', 'g' ) || '@gmail.com' ELSE LOWER(REPLACE(TRIM(email), ' ', '')) END AS normalized_email FROM users ) AS cleaned;
🔍 Как это работает:
LOWER(TRIM(email)) — убираем пробелы и регистр
SPLIT_PART(..., '+', 1) — отрезаем всё после +
REGEXP_REPLACE(..., '\.', '', 'g') — удаляем точки
Считаем DISTINCT, чтобы получить число уникальных email'ов
🔥 Используй такие трюки для: • антифрода • чистки базы • аналитики поведения пользователей
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How Does Bitcoin Work?
Bitcoin is built on a distributed digital record called a blockchain. As the name implies, blockchain is a linked body of data, made up of units called blocks that contain information about each and every transaction, including date and time, total value, buyer and seller, and a unique identifying code for each exchange. Entries are strung together in chronological order, creating a digital chain of blocks. “Once a block is added to the blockchain, it becomes accessible to anyone who wishes to view it, acting as a public ledger of cryptocurrency transactions,” says Stacey Harris, consultant for Pelicoin, a network of cryptocurrency ATMs. Blockchain is decentralized, which means it’s not controlled by any one organization. “It’s like a Google Doc that anyone can work on,” says Buchi Okoro, CEO and co-founder of African cryptocurrency exchange Quidax. “Nobody owns it, but anyone who has a link can contribute to it. And as different people update it, your copy also gets updated.”
