RAID serves for two data storage requirements
->Reliability-It maintains multiple copies of same data in
array of disks to make the storage fault tolerant in case of
->Performance-Different bits of a data component is stored
across an array of disks(bit striping) so that access time
is greatly reduced since single read time is enough to read
all the bits since they are in different disks, thus
boosting the performance.
using commit command
For All SQL , Tested in PostgresSQL : Javedcc@gmail.com
SELECT * FROM <Table_Name> A
WHERE N = (SELECT COUNT(DISTINCT B.Column_Name ) FROM
<Table_Name> B WHERE A.Column_Name >= B.Column_Name)
Over 200. As with other open source projects, of course, we depend on hundreds of community members for documentation, translations, advocacy, conferences, website development, infrastructure, and peer-to-peer support.
wide distribution through the open source world and liberal licensing make that a difficult question to answer with any accuracy. A previous version, 8.0, had an estimated one million downloads within a seven months of release. However, most users get PostgreSQL with a Linux distribution, or with some of the many other products, OSS software, and hardware devices that include PostgreSQL.
None. PostgreSQL is an unincorporated association of volunteers and companies who share code under the PostgreSQL License.
This is a topic that can start several hours of discussion. As a quick summary, MySQL is the "easy-to-use, web developer" database, and PostgreSQL is the "feature-rich, standards-compliant" database. PostgreSQL is liberally licensed and owned by its community; MySQL is GPL-licensed and owned by Oracle. Beyond that, each database user should make his own evaluation; open source software makes doing comparisons very easy.
Our feature set is generally considered to be very competitive with other leading SQL RDBMSes. Certainly there are features some of them have which we don't, and the reverse is also true. To date, only a few benchmarks have been published showing PostgreSQL to be within 10-30% of proprietary competitors. However, we have had many users migrate from other database systems - primarily Oracle and Informix - and they are completely satisfied with the performance of their PostgreSQL systems.
The term "NoSQL" covers such a diverse array of non-relational database implementations ... from tiny embedded databases like TokyoCabinet to massive clustered data processing platforms like Hadoop ... that it's impossible to comment on them as a general class. Non-relational databases preceded relational databases and have existed alongside them for forty years, so choosing between relational and nonrelational databases is nothing new. Users should choose the database whose features, implementation, and community support their current application needs. Further, using multiple different databases for large projects is fast becoming the norm, and PostgreSQL users are no exception.