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100 means 100 bps (bits per second). This is the data transfer speed for cables.
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Friday, March 28, 2008
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A database index is a data structure that improves the speed of operations in a table. Indices can be created using one or more columns,
providing the basis for both rapid random lookups and efficient
ordering of access to records. The disk space required to store the
index is typically less than the storage of the table (since indices
usually contain only the key-fields according to which the table is to
be arranged, and excludes all the other details in the table), yielding
the possibility to store indices into memory from tables that would not
fit into it. In a relational databasean index is a copy of part of a table. Some databases extend the power
of indexing by allowing indices to be created on functions or expressions. For example, an index could be created on upper(last_name),
which would only store the uppercase versions of the last_name field in
the index. Another option sometimes supported is the use of "filtered"
indices, where index entries are created only for those records that
satisfy some conditional expression. A further aspect of flexibility is
to permit indexing on user-defined functions, as well as expressions formed from an assortment of built-in functions.
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Monday, April 28, 2008
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