Changes between Version 4 and Version 5 of waue/2010/0128


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Timestamp:
Jan 29, 2010, 6:01:17 PM (15 years ago)
Author:
waue
Comment:

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  • waue/2010/0128

    v4 v5  
    1111= what is secondary index (distinguished to primary index) =
    1212
    13 Explain what is primary and secondary index.
     13indexing with another field which is not primary key.
     14
     15內容與原本table 相似的另一張table,但key 不同,利於排列內容
     16
     17如: table1 (primary)
     18 ||   || '''name''' || '''price'''  || '''description'''  ||
     19 || 1 || apple || 10 || xxx ||
     20 || 2 || orig || 5 || ooo ||
     21 || 3 || banana || 15 || vvvv ||
     22 || 4 || tomato || 8 || uuuu ||
     23
     24使用者想依售價做排序,則可以建立 secondary index table
     25 ||  '''price'''   || '''name''' || '''description'''  ||
     26 || 5 || orig  || ooo ||
     27 || 8 || tomato || uuuu ||
     28 || 10 || apple || xxx ||
     29 || 15 || banana  || vvvv ||
     30
     31
     32 == Explain what is primary and secondary index ==
    1433
    1534When you activate an object say ODS / DSO, the system automatically generate an index based on the key fields and this is primary index.