--清空查询分析器的缓存
dbcc dropcleanbuffers
SELECT fas_id,fas_theme from tempA where fas_theme<>'' --查询开销最大
SELECT fas_id,fas_theme from tempA where fas_theme>‘’ --前提是处理过isnull(fas_theme,'') as fas_theme Into 临时表tempA 里面,
SELECT fas_id,fas_theme from tempA where len(fas_theme)>0 --在执行过清理缓存的时候再执行此语句会慢,不执行清理缓存时,联系查询,第2次比第1次快