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#1
 
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index -
07-28-2008
, 09:13 AM
#2
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Hi all, I read the following in a book 1) we can have several non clustered indexes on a table , but we can have only one clustered index per table 2) index on the primary key can be clustered or non clustered now my question is To what extent these statements are true ? |
The above two statements are true for sybase ASE. I think that the first is
true for most RDBMS although the terminology may differ. (Oracle index
organized table = ASE clustered index.)
#3
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Hi all, I read the following in a book 1) we can have several non clustered indexes on a table , but we can have only one clustered index per table 2) index on the primary key can be clustered or non clustered now my question is To what extent these statements are true ? |
The above two statements are true for sybase ASE. I think that the first is
true for most RDBMS although the terminology may differ. (Oracle index
organized table = ASE clustered index.)
#4
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Hi all, I read the following in a book 1) we can have several non clustered indexes on a table , but we can have only one clustered index per table 2) index on the primary key can be clustered or non clustered now my question is To what extent these statements are true ? |
The above two statements are true for sybase ASE. I think that the first is
true for most RDBMS although the terminology may differ. (Oracle index
organized table = ASE clustered index.)
#5
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Hi all, I read the following in a book 1) we can have several non clustered indexes on a table , but we can have only one clustered index per table |
rowid's. When accessing the table through the index you first look up
the rowid's that correspond to the key-value(s) you're looking for and
then use the rowid's to retrieve the records from the actual table.
With a clustered index, the index is not separate from the table, but
the records of the table are stored in the order of the index-key. This
means that when you lookup records through a clustered index you can
directly look into the table using the key-values you need.
Since you can store the records only in one order, you can have only one
clustered index per table.
Quote:
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2) index on the primary key can be clustered or non clustered |
discriminate between candidate keys. Primary keys are a construct
stemming from implementation issues. If I recall correctly early RDBMS's
used the primary key to determine the storage order of records, thus
making it a clustered index.
Nowadays, many RDMS's allow to cluster on other keys.
#6
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Hi all, I read the following in a book 1) we can have several non clustered indexes on a table , but we can have only one clustered index per table |
rowid's. When accessing the table through the index you first look up
the rowid's that correspond to the key-value(s) you're looking for and
then use the rowid's to retrieve the records from the actual table.
With a clustered index, the index is not separate from the table, but
the records of the table are stored in the order of the index-key. This
means that when you lookup records through a clustered index you can
directly look into the table using the key-values you need.
Since you can store the records only in one order, you can have only one
clustered index per table.
Quote:
|
2) index on the primary key can be clustered or non clustered |
discriminate between candidate keys. Primary keys are a construct
stemming from implementation issues. If I recall correctly early RDBMS's
used the primary key to determine the storage order of records, thus
making it a clustered index.
Nowadays, many RDMS's allow to cluster on other keys.
#7
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Hi all, I read the following in a book 1) we can have several non clustered indexes on a table , but we can have only one clustered index per table |
rowid's. When accessing the table through the index you first look up
the rowid's that correspond to the key-value(s) you're looking for and
then use the rowid's to retrieve the records from the actual table.
With a clustered index, the index is not separate from the table, but
the records of the table are stored in the order of the index-key. This
means that when you lookup records through a clustered index you can
directly look into the table using the key-values you need.
Since you can store the records only in one order, you can have only one
clustered index per table.
Quote:
|
2) index on the primary key can be clustered or non clustered |
discriminate between candidate keys. Primary keys are a construct
stemming from implementation issues. If I recall correctly early RDBMS's
used the primary key to determine the storage order of records, thus
making it a clustered index.
Nowadays, many RDMS's allow to cluster on other keys.
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