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小整理一下魚缸 April 15, 2007

Posted by Jeff in : Aquarium , 2 comments

因為魚飼料吃完了
那天帶霓寶去水族店逛逛
就帶了幾隻藻蝦
還有霓寶挑的草莓麗麗
也順便買了一些草來 refresh 一下魚缸

2007.04.07 (by Jeff Yeh)
更新之後的樣子, 看起來比之前的豐富一些

大和藻蝦 (by Jeff Yeh) 草莓麗麗 (by Jeff Yeh)
新朋友-大和藻蝦和草莓麗麗
DSC09939 (by Jeff Yeh)
沒啥在顧 卻生的一堆的小蝦

Oracle optimizer April 4, 2007

Posted by Jeff in : oracle , add a comment

基本上大多是用 CBO (Costed Based Optimize)
不過遇到有些 RBO 的狀況
還是得乖乖照著玩

RBO (Rule Based Optimize)
1 ROWID = constant
2 Cluster join with unique or primary key = constant
3 Hash cluster key with unique or primary key = constant
4 Entire Unique concatenated index = constant
5 Unique indexed column = constant
6 Entire cluster key = corresponding cluster key of another table in the same cluster
7 Hash cluster key = constant
8 Entire cluster key = constant
9 Entire non-UNIQUE CONCATENATED index = constant
10 Non-UNIQUE index merge
11 Entire concatenated index = lower bound
12 Most leading column(s) of concatenated index = constant
13 Indexed column between low value and high value or indexed column LIKE “ABC%” (bounded range)
14 Non-UNIQUE indexed column between low value and high value or indexed column like `ABC%’ (bounded range)
15 UNIQUE indexed column or constant (unbounded range)
16 Non-UNIQUE indexed column or constant (unbounded range)
17 Equality on non-indexed = column or constant (sort/merge join)
18 MAX or MIN of single indexed columns
19 ORDER BY entire index
20 Full table scans

* Oracle 10g 已經沒有 RBO 了, 雖然你還是可以用, 不過 Oracle 強調他提供 RBO 只是為了向下相容的考量