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The main content of this article is to explain "what is SQL Server". Interested friends may wish to take a look. The method introduced in this paper is simple, fast and practical. Let's let the editor take you to learn what SQL Server is.

The version of SQLServer

It was originally developed by Microsoft, Sybase and Ashton-Tate, and the first OS/2 version was launched in 1988. In 1996, Microsoft launched SQL Server version 6.5. in 1998, SQL Server version 7.0was released to users. SQL Server 2000 was launched by Microsoft in 2000 and is currently the latest version of SQL SERVER 2016.

The version of Oracle also began to follow this routine. 9iMagne10g, 11g, 12c, down is 18, because from 2018, the version number of Oracle database will jump directly to 18.

Gant Magic Quadrant

If Oracle is the most powerful business database, it is estimated that there will be few opposing voices. Oracle has been in this powerful halo over the years, but from the development in recent years, SQL Server has also changed a lot, until last year when it looked at the magic quadrant of Garnter, it even reached the first place.

This quadrant is a conclusion made through multiple dimensions, so it is a comprehensive advantage.

The ranking of DB engines

I got the latest database popularity ranking from DB Engines, and the top three are still Oracle,MySQL,SQL Server, and from my one-sided understanding, SQL Server doesn't seem to be as hot as he should be.

If you take a closer look at the database product competition chart and the customer flow diagram, you will find that many databases are shrinking. In my impression, SQL Server is relatively widely used in South Korea and Taiwan.

The thick line in the middle is Oracle to MySQL. The following figure needs to be added, that is, from Oracle to SQL Server, Microsoft has launched a database version of the Linux platform, which is a great addition to the development of Azure, and Microsoft has invested a lot of human and financial resources to dilute Oracle's market share. They launched a free strategy to migrate SQL Server to Oracle. In addition to the free SQL Server license, Microsoft also provides free SQL Server technical training and compensation to offset the cost of migration deployment. Of course, this policy has a certain timeliness.

MVP

Microsoft also spends a lot of energy on the community. Their community experts are called MVP, and they are selected through selection. The whole entry criteria are a bit similar to Oracle's ACE, and they will send trophies and so on after getting honors.

Installation type

There are many installation types of SQL Server, including enterprise version, standard version, individual version, development version, enterprise evaluation version and so on. It is estimated that some have not been sorted out carefully, from the version of the price point of view, slightly lower than Oracle, there is a certain gradient price between versions.

There are relatively few versions of Oracle, such as Enterprise Edition, Standard Edition, and an intermediate version. The difference in version is the difference in components. Such as ADG,RAC,Partition, these are all enterprise versions.

The difference of MySQL in this respect is more obvious. Commercial version, community version, MariaDB,Percona,Drizzle..., except for a basic fee for commercial version, are all free and open source. Of course, this comparison is unfair. After all, it is commercial database and open source database.

System structure

It is especially important to learn a database and look at its architectural design. This is an architecture diagram I found.

Overall, the database engine is divided into the following four parts.

Protocol layer (Protocols)

At this level, SQL Server is very comprehensive, supporting TCP/IP,name pipes, etc., Oracle's network service is independent, the native is bequeath protocol, network TCP. Network expansion support is strong, support multi-port, a variety of configuration modes.

MySQL is simpler in this respect, with a single port and a unified protocol.

Relational engine (Relational Engine), also known as query processor (Query Processor)

This is called one of the most complex components of SQL Server. It is similar to what we usually call the SQL engine.

Storage engine (Storage Engine)

The components of the storage engine are generally transaction services, lock managers, access methods and utilities.

The storage engine in MySQL lets a hundred flowers blossom, especially InnoDB.

SQLOS is the application layer, is the lowest layer, there are a lot of scheduling and management, such as memory management, deadlock detection, scheduling and so on.

Isolation level

SQL Server has the following five levels of transaction isolation, one more than we usually say: snapshots.

Read Uncommitted: only pessimistic concurrency is supported

Repeatable Read: only pessimistic concurrency is supported

Serializable: only pessimistic concurrency is supported

Snapshot: supports optimistic concurrency

Read Committed: default isolation level, which supports both pessimistic and optimistic concurrency depending on configuration

Backup and recovery

This work, if done manually, can be done through a graphical interface, which many databases can not achieve the ease of use and user experience of SQL Server. Of course, high-volume environments should be implemented in scripts.

Look at the sentence of SQL Server create database, and Oracle would like to, some data dictionaries will also be very similar. For example, there are information_schema, sys and so on.

At this point, I believe you have a deeper understanding of "what SQL Server is", might as well come to the actual operation of it! Here is the website, more related content can enter the relevant channels to inquire, follow us, continue to learn!

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