悠人小筑

Don't be yourself tierd.Learn how to give up.

In a word,living for yourself.

Today is the last day of the year 2008,tomorrow is a newer day.

enjoy life,relax yourself.

have a good day.

 

there are two days left for year 2008.Tonight it's strange quiet.It's very cold and the wind is blowing.

everything falls sleeps.listening music,calm down, tomorrow will be fine.

The sun is rising.

时间好快啊,一年又快过去了.今天是小年了,不过没有过年的气氛.今天下午和同事一起去逛了超市,发现了一些好东西.感觉自己还像个小孩子一样,然后就买了一个个"小牛",一个小熊.不知道他们俩个会不会吵架.不过最好不要,和和美美才是真嘛.有他们俩做伴今年应该不会难过吧

 

 

 

 

Today it's wam,it feels good.After having the breakfirst,I decide to go to work on foot. the cold days lasted almost one week.

Left and right,right and left,you can see the birds flying,after half an hour,I got to the company.

It feels great.It's cool.

What a lovely day!

It's the last day of the year 2008.wish betther the next year.

little by little,it will be fine.

Table Access Costs:

• Number of blocks/MbDivisor
  • MbDivisor (multi block read divisor) is multi_block_readcount for <9.2v
  • For Oracle >=9.2, if the system statistics are collected, Oracle will estimate it
  • To find out what it is estimated to, run a simple query with the single table access path and then divide "NBLKS:/"Resc:"

Index access costs:

• Unique scan: blevel + 1
• Fast full scan: leaf_ blocks / MbDivisor
• Full scan: Num_blocks/MbDivisor
• Index: blevel + FF* leaf_ blocks
• Range scan: blevel + FF* leaf_ blocks + FF* clustering_ factor
  • FF is a Filtering Factor, which is either the density if "=" is used or a formula depending on the predicate.

Join access costs:

• NL join: COST(outer) + [ CARD(outer) * COST(inner)]
• Merge join: Resc(outer) + Resc(inner) + Sort_Cost(outer) + Sort_Cost(inner)
• Hash join: Resp(outer) + Resp(inner) + Par_Sort_Cost(outer) + Par_Sort_Cost(inner)

Note that if the index does not have statistics, you will get the default numbers in the file. The default stats for LEAF_BLOCKS=25, BLEVEL=1, DISTINCT_KEYS=100 and CLUSTERING_FACTOR=800.For a table, you will get a message that the table is not analyzed. Default assumptions for a table are: 100 block, 100 rows, even data distribution.

好久都没有更新了，不知道自己该做些什么?感觉自己好失败哦，what I should do