How dbms like Oracle, MySql and Sql Server manage "free space"? [closed] - mysql

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Closed 11 years ago.
thish is a general question about the "big" database player.
I want to know how these DBMS manage deleted record. In particular: does they free space and re-utilize that free space ?
Hope not to be off topic.
Thank you!

In general, they mark a deleted record as deleted, and they keep track of how much free space is available (and where), and will reuse the storage eventually (for new or updated records), but not necessarily in a timely manner.

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Maximum hits on a table in MySQL [closed]

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Closed 10 years ago.
I need to do some analysis of table usage within my MySQL system. Can anyone point me in the right direction on a method for identifying which table has been queried most often in a given time-period i.e. if there are 30 tables, I want to know which table is accessed most.
You should use pt-table-usage to analyze the general query log. It will out put nice information about table usage (as long as you're not using stored procedures or stored functions cause those will be missed).
Enable query logging temporarily while your application is running and review the log. It can have some performance impact, so you don't want to leave it permanently enabled.

WebGraph storage in Relational Databases [closed]

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Closed 10 years ago.
How one can efficiently store the WebGraph in Relational databases such MySQL for playing with algorithms like PageRank? I think of creating two tables: one for URLs where only distinct URLs will be stored and another outgoing links table, for each url store its outgoing URL. Any ideas or any suggestions for efficient storage?
There are specific databases which where created for such a purpose. Take a look at
http://neo4j.org/
https://launchpad.net/giraffedb

Best Way To Store Roster In SQL Database [closed]

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Closed 11 years ago.
I'm working on a roster system for my workplace and was wondering what the best way of storing roster information in the database would be i.e there are staff members already in the database, and every staff member would have roster information for each day that there is a shift rostered to them - similar to findmyshift.com.
You haven't really given us enough information to go on. However. Barry Williams's library of free data models has a simple model for a Nurses' Roster, which you could adapt for your needs. Find it here.

What did Index Means in DB? [closed]

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Closed 12 years ago.
Whats does "indexing" mean? How it is useful to a web crawler?
Internal indexing in a database and the index that a web crawler looks at are two different concepts.
Indexing in a database is a method to make looking up records by certain columns faster.
Indexing in the context of web crawlers involves storing web pages and building an index based on what's in them so as to access them by content more easily.
http://en.wikipedia.org/wiki/Index_(database)
http://en.wikipedia.org/wiki/Web_indexing

On-premise, off-premise applications, what are they? [closed]

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Closed 9 years ago.
When I study about cloud-computing, I usually see these terms: on-premise, off-premise applications. I tried to search them on Google, but no luck. Can anyone please explain these terms to me?
On premises means on location, whereas off premises means remote (in the cloud). For instance if an application runs on an "on-premises" server it means the server is physically in the company. If you have an off-premises solution it's hosted in the cloud or centralized location.
you can always check wikipedia for explanation of technical terms:
http://en.wikipedia.org/wiki/On-premises_software
http://en.wikipedia.org/wiki/Cloud_computing