Data Science. SQL hub
По всем вопросам- @workakkk @itchannels_telegram - 🔥лучшие ит-каналы @ai_machinelearning_big_data - Machine learning @pythonl - Python @pythonlbooks- python книги📚 @datascienceiot - ml книги📚 РКН: https://vk.cc/cIi9vo #VRHSZ
Show more📈 Analytical overview of Telegram channel Data Science. SQL hub
Channel Data Science. SQL hub (@sqlhub) in the Russian language segment is an active participant. Currently, the community unites 36 137 subscribers, ranking 3 717 in the Technologies & Applications category and 17 613 in the Russia region.
📊 Audience metrics and dynamics
Since its creation on невідомо, the project has demonstrated rapid growth, gathering an audience of 36 137 subscribers.
According to the latest data from 26 October, 2026, the channel demonstrates stable activity. Although there has been a change in the number of participants by 181 over the last 30 days and by -9 over the last 24 hours, overall reach remains high.
- Verification status: Not verified
- Engagement rate (ER): The average audience engagement rate is 8.14%. Within the first 24 hours after publication, content typically collects 3.93% reactions from the total number of subscribers.
- Post reach: On average, each post receives 2 941 views. Within the first day, a publication typically gains 1 422 views.
- Reactions and interaction: The audience actively supports content: the average number of reactions per post is 9.
- Thematic interests: Content is focused on key topics such as sql, индекс, postgres, index, sqlite.
📝 Description and content policy
The author describes the resource as a platform for expressing subjective opinions:
“По всем вопросам- @workakkk
@itchannels_telegram - 🔥лучшие ит-каналы
@ai_machinelearning_big_data - Machine learning
@pythonl - Python
@pythonlbooks- python книги📚
@datascienceiot - ml книги📚
РКН: https://vk.cc/cIi9vo
#VRHSZ”
Thanks to the high frequency of updates (latest data received on 27 October, 2026), the channel maintains relevance and a high level of publication reach. Analytics show that the audience actively interacts with content, making it an important point of influence in the Technologies & Applications category.
SELECT DISTINCT u.id, u.name
FROM users u
JOIN orders o ON o.user_id = u.id
WHERE o.created_at >= CURRENT_DATE - INTERVAL '30 days';
Лучше так:
SELECT u.id, u.name
FROM users u
WHERE EXISTS (
SELECT 1
FROM orders o
WHERE o.user_id = u.id
AND o.created_at >= CURRENT_DATE - INTERVAL '30 days'
);
DISTINCT часто добавляет sort или hash aggregation на огромном объёме.
EXISTS превращает задачу в semijoin:
• оптимизатору проще остановиться на первом совпадении
• меньше памяти, меньше лишних строк, стабильнее план
Это один из тех рефакторингов, который на больших таблицах реально даёт заметный буст.
SELECT DISTINCT u.id, u.name
FROM users u
JOIN orders o ON o.user_id = u.id;
Лучше так:
SELECT u.id, u.name
FROM users u
WHERE EXISTS (
SELECT 1
FROM orders o
WHERE o.user_id = u.id
);
Почему это сильный приём:
EXISTS останавливается, как только находит первое совпадение
не нужно тащить лишние строки
не нужно потом убирать дубли
логика запроса становится честной - ты проверяешь наличие, а не собираешь мусор
Это один из самых частых hidden performance fixes в SQL. Если видишь DISTINCT, сразу спрашивай себя: он тут реально нужен или просто маскирует плохую логику JOIN.