优化查询 common.DB.Raw("SELECT count(*) FROM(SELECT id,created_at,schedule,content,url FROM records WHERE pm_id = ? AND status = 2 AND deleted_at is Null "+ " UNION SELECT id,created_at,content FROM supervisings WHERE pm_id = ? AND deleted_at is Null "+ " UNION SELECT id,created_at,content FROM instructions WHERE pm_id = ? AND deleted_at is Null "+")"+ "AS combined_tables", code, code, code).Scan(&count)
时间: 2024-04-09 14:33:41 浏览: 15
你可以对这个查询进行一些优化,以提高性能和可读性。以下是一种可能的优化方式:
```go
// 将原始的 SQL 查询语句拆分为多个子查询
subQuery1 := common.DB.Raw("SELECT id, created_at, schedule, content, url FROM records WHERE pm_id = ? AND status = 2 AND deleted_at IS NULL", code)
subQuery2 := common.DB.Raw("SELECT id, created_at, content FROM supervisings WHERE pm_id = ? AND deleted_at IS NULL", code)
subQuery3 := common.DB.Raw("SELECT id, created_at, content FROM instructions WHERE pm_id = ? AND deleted_at IS NULL", code)
// 使用 UNION ALL 替代 UNION,因为 UNION ALL 不会去重
combinedQuery := common.DB.Raw("SELECT COUNT(*) FROM (? UNION ALL ? UNION ALL ?) AS combined_tables", subQuery1, subQuery2, subQuery3)
// 执行查询并将结果存储到 count 变量中
combinedQuery.Scan(&count)
```
通过将查询拆分为更小的子查询,并使用 UNION ALL 替代 UNION,可以提高查询的性能。此外,使用命名的子查询可以使代码更易读和维护。请注意,这只是一种优化方式,具体的优化方法可能因数据库和数据模型的特点而有所不同。在实际应用中,你可以根据具体情况进行调整和测试,以获得最佳性能。