编写SQL数据提取查询

SELECT *
FROM app_events
WHERE event = 'login'
  AND event_date >= '2025-09-01'
  AND country = 'CN';

说明：
- 若event_date为TIMESTAMP类型，建议使用'2025-09-01 00:00:00'以明确时间起点。

SELECT *
FROM users
WHERE app_version = '3.2.1'
  AND channel IN ('organic', 'ads')
  AND is_active = 1;

以下为满足条件的SQL查询，并根据常见数据库的布尔类型差异给出两种写法：

1) 适用于MySQL/SQLite（布尔型常用TINYINT/INTEGER，1表示真）
SELECT *
FROM user_campaigns
WHERE campaign_id = 101
  AND joined = 1
  AND repurchased = 1;

2) 适用于PostgreSQL（原生布尔型）
SELECT *
FROM user_campaigns
WHERE campaign_id = 101
  AND joined = TRUE
  AND repurchased = TRUE;

可选优化建议（高选择性过滤时有助于查询性能）：
- 建立复合索引：(campaign_id, joined, repurchased)
- 若joined/repurchased允许NULL且希望仅匹配明确的“真”，上述条件已自然排除NULL；如需包含NULL情形，请根据业务语义调整过滤条件。