SQLServer性能优化一则小实例

首先找到 最耗CPU的top50 SQL------------------------------------------SELECT total_cpu_time, total_execution_count, number_of_statements, s2.text --(SELECT SUBSTRING(s2.text, statement_start_offset / 2, ((CASE WHEN statement_end_offset = -1 THEN (LEN(CONVERT(NVARCHAR(MAX), s2.text)) * 2) ELSE statement_end_offset END) - statement_start_offset) / 2) ) AS query_textFROM (SELECT TOP 50 SUM(qs.total_worker_time) AS total_cpu_time, SUM(qs.execution_count) AS total_execution_count, COUNT(*) AS number_of_statements, qs.sql_handle --, --MIN(statement_start_offset) AS statement_start_offset, --MAX(statement_end_offset) AS statement_end_offset FROM sys.dm_exec_query_stats AS qs GROUP BY qs.sql_handle ORDER BY SUM(qs.total_worker_time) DESC) AS stats CROSS APPLY sys.dm_exec_sql_text(stats.sql_handle) AS s2------------------------------------------------------------------------------------------------有一条SQL执行效率非常差，大概30秒~80秒不等，而且占据了所有CPU消耗时间的20%，并且执行次数也很多select f_getconcatname(id) from table where id>1 and id<100如果单个ID，速度还是很快的，初步判断是ID未作索引的问题后来查看了一下该表的定义，已经做了索引，索引可以排除掉在接着判断是函数的问题查看了一下函数的定义，这个只是大概的函数create function f_getconcatname(@id)asDECLARE cur_concat CURSOR FOR SELECT Name FROM tableB where id=@iddeclare @ret varchar(200),@tmp varchar(20)set @ret='';set @tmp=''OPEN cur_concatFETCH NEXT FROM cur_concat into @tmpWHILE @@FETCH_STATUS = 0BEGIN set ret=@ret+@tmp+',' FETCH NEXT FROM cur_concat into @tmpENDCLOSE contact_cursorDEALLOCATE contact_cursorend原以为是函数内游标循环太慢就修改了一下该函数create function f_getconcatname(@id)asdeclare @ret varchar(200)set @ret='';SELECT @ret=@ret+Name+',' FROM tableB where id=@idreturn @retend没想到竟然比游标还慢后来检查了一下tableB关于ID的定义，发现ID没有定义为索引添加索引后再次尝试，发现速度提高到0~1秒OK，解决该问题同时在CPU 消耗总量的TOP 50中居然有25问题与之有关，一连串顺带解决了25个问题