随随便便来一个问题sql

达梦数据库用于验证耗时和临时空间消耗

select count(0) from (select DISTINCT A.ID,c.NAME, b.CRTDATE from (select * from sysobjects where rownum<501) a,(select * from sysobjects where rownum<501) b,(select * from sysobjects where rownum<51) c order by a.id desc);

预计耗时15秒，消耗temp 空间500MB

SELECT  TOP 20  EXEC_ID,   substr( SQL_TEXT,1,50) txt,    MTAB_USED_BY_M,MTAB_TYPE
FROM  V$MTAB_USED_HISTORY ORDER BY  MTAB_USED_BY_M DESC;

战绩可查：