面试问题

wkc168

sql1 全表扫描了两次
sql2  表扫描了1次

opsdba

Still not answer the question,  what you show the result was given, tell WHY #2 better man.

Yong Huang

原帖由 opsdba 于 2010-9-15 05:32 发表
Still not answer the question,  what you show the result was given, tell WHY #2 better man.

Not sure what you're asking. Perhaps this from msg #4 answers your question?

"It [the second query] has only half of the first SQL's consistent gets due to one time (instead of twice) of scanning table EMP."

Yong Huang

opsdba

Let back to the original question, what they asked: "问：这两条语句的2效率为什么比1高"

you don't need check what they given, but answer the "WHY=这两条语句的2效率为什么比1高"

read the question carefully!


Not sure what you're asking. Perhaps this from msg #4 answers your question?

"It [the second query] has only half of the first SQL's consistent gets due to one time (instead of twice) of scanning table EMP."

Yong Huang [/quote]