Update from Sync Service

数据库/Cpu 占用过高.md

@@ -1,15 +1,54 @@
+# CPU 占用过高排查
+
+> SQL Server 查询最耗 CPU 的 SQL 语句
+
+## 查询最耗 CPU 的语句
+
 ```sql
 SELECT TOP 10
-```
+    total_worker_time / execution_count AS avg_cpu_cost,
-total_worker_time/execution_count AS avg_cpu_cost, plan_handle,
+    plan_handle,
-execution_count,
+    execution_count,
-(SELECT SUBSTRING(text, statement_start_offset/2 + 1,
+    (SELECT SUBSTRING(
-(CASE WHEN statement_end_offset = -1
+        text,
-THEN LEN(CONVERT(nvarchar(max), text)) * 2
+        statement_start_offset / 2 + 1,
-ELSE statement_end_offset
+        (CASE
-```sql
+            WHEN statement_end_offset = -1
-END - statement_start_offset)/2)
+            THEN LEN(CONVERT(nvarchar(max), text)) * 2
-FROM sys.dm_exec_sql_text(sql_handle)) AS query_text
+            ELSE statement_end_offset
+        END - statement_start_offset) / 2
+    ) FROM sys.dm_exec_sql_text(sql_handle)) AS query_text
 FROM sys.dm_exec_query_stats
+ORDER BY [avg_cpu_cost] DESC
 ```
-ORDER BY [avg_cpu_cost] DESC
+
+## 常用排查命令
+
+```sql
+-- 查看当前会话
+EXEC sp_who2
+
+-- 查看锁
+EXEC sp_lock
+
+-- 查看 CPU 使用
+SELECT 
+    session_id,
+    status,
+    cpu_time
+FROM sys.dm_exec_requests
+ORDER BY cpu_time DESC
+```
+
+## 常见原因
+
+| 原因 | 解决方法 |
+|------|----------|
+| 缺少索引 | 添加适当索引 |
+| 统计信息过时 | UPDATE STATISTICS |
+| 低效查询 | 优化 SQL |
+| 过多编译 | 使用参数化查询 |
+
+---
+
+> 💡 定期检查慢查询，持续优化。