Microsoft SQL Server - Wikipedia, the free encyclopedia. Microsoft SQL Server. Developer(s)Microsoft. Initial release. April 2.
SQL Server 1. 0. Stable release. SQL Server 2. 01. June 1, 2. 01. 6; 3 months ago (2. Development status. Active. Written in. C, C++Operating system. Microsoft Windows, Windows Server, Linux (beta in March 2. As a database server, it is a software product with the primary function of storing and retrieving data as requested by other software applications. SQL Server 4. 2 was shipped in 1. OS/2 version 1. 3, followed by version 4. Windows NT, released alongside Windows NT 3. SQL Server 6. 0 was the first version designed for NT, and did not include any direction from Sybase. About the time Windows NT was released in July 1. Sybase and Microsoft parted ways and each pursued its own design and marketing schemes. Microsoft negotiated exclusive rights to all versions of SQL Server written for Microsoft operating systems. All operations that can be invoked on SQL Server are communicated to it via a Microsoft- defined format, called Tabular Data Stream (TDS). TDS is an application layer protocol, used to transfer data between a database server and a client. Initially designed and developed by Sybase Inc. SQL Server Connection Strings. You can get to the Activity Monitor in SQL Server Management Studio by. It will appear int he program How do I open SQL Server Management Studio? SQL Server 2008 Management Studio Express. The program you are about to. Sql Server Management Studio Program NamesConsequently, access to SQL Server is available over these protocols. In addition, the SQL Server API is also exposed over web services. SQL Server supports different data types, including primary types such as Integer, Float, Decimal, Char (including character strings), Varchar (variable length character strings), binary (for unstructured blobs of data), Text (for textual data) among others. The rounding of floats to integers uses either Symmetric Arithmetic Rounding or Symmetric Round Down (fix) depending on arguments: SELECT Round(2. Microsoft SQL Server also allows user- defined composite types (UDTs) to be defined and used. It also makes server statistics available as virtual tables and views (called Dynamic Management Views or DMVs). In addition to tables, a database can also contain other objects including views, stored procedures, indexes and constraints, along with a transaction log. A SQL Server database can contain a maximum of 2. OS- level files with a maximum file size of 2. Secondary data files, identified with a . Log files are identified with the . A page is the basic unit of I/O for SQL Server operations. A page is marked with a 9. ID of the object that owns it. Page type defines the data contained in the page: data stored in the database, index, allocation map which holds information about how pages are allocated to tables and indexes, change map which holds information about the changes made to other pages since last backup or logging, or contain large data types such as image or text. While page is the basic unit of an I/O operation, space is actually managed in terms of an extent which consists of 8 pages. A database object can either span all 8 pages in an extent (. A row in a database table cannot span more than one page, so is limited to 8 KB in size. However, if the data exceeds 8 KB and the row contains varchar or varbinary data, the data in those columns are moved to a new page (or possibly a sequence of pages, called an allocation unit) and replaced with a pointer to the data. The partition size is user defined; by default all rows are in a single partition. Sql Server Management Studio Program Name For SystemA table is split into multiple partitions in order to spread a database over a computer cluster. Rows in each partition are stored in either B- tree or heap structure. If the table has an associated, clustered index to allow fast retrieval of rows, the rows are stored in- order according to their index values, with a B- tree providing the index. The data is in the leaf node of the leaves, and other nodes storing the index values for the leaf data reachable from the respective nodes. If the index is non- clustered, the rows are not sorted according to the index keys. An indexed view has the same storage structure as an indexed table. A table without a clustered index is stored in an unordered heap structure. However, the table may have non- clustered indices to allow fast retrieval of rows. In some situations the heap structure has performance advantages over the clustered structure. Both heaps and B- trees can span multiple allocation units. Any 8 KB page can be buffered in- memory, and the set of all pages currently buffered is called the buffer cache. The amount of memory available to SQL Server decides how many pages will be cached in memory. The buffer cache is managed by the Buffer Manager. Either reading from or writing to any page copies it to the buffer cache. Subsequent reads or writes are redirected to the in- memory copy, rather than the on- disc version. The page is updated on the disc by the Buffer Manager only if the in- memory cache has not been referenced for some time. While writing pages back to disc, asynchronous I/O is used whereby the I/O operation is done in a background thread so that other operations do not have to wait for the I/O operation to complete. Each page is written along with its checksum when it is written. When reading the page back, its checksum is computed again and matched with the stored version to ensure the page has not been damaged or tampered with in the meantime. As such, it needs to control concurrent access to shared data, to ensure data integrity. SQL Server provides two modes of concurrency control: pessimistic concurrency and optimistic concurrency. When pessimistic concurrency control is being used, SQL Server controls concurrent access by using locks. Locks can be either shared or exclusive. Exclusive lock grants the user exclusive access to the data. Shared locks are used when some data is being read. The latter would have to wait for all shared locks to be released. Locks can be applied on different levels of granularity. For indexes, it can either be on the entire index or on index leaves. The level of granularity to be used is defined on a per- database basis by the database administrator. While a fine grained locking system allows more users to use the table or index simultaneously, it requires more resources. So it does not automatically turn into higher performing solution. SQL Server also includes two more lightweight mutual exclusion solutions. SQL Server uses them for DMVs and other resources that are usually not busy. SQL Server also monitors all worker threads that acquire locks to ensure that they do not end up in deadlocks. The Lock Manager maintains an in- memory table that manages the database objects and locks, if any, on them along with other metadata about the lock. Access to any shared object is mediated by the lock manager, which either grants access to the resource or blocks it. SQL Server also provides the optimistic concurrency control mechanism, which is similar to the multiversion concurrency control used in other databases. The mechanism allows a new version of a row to be created whenever the row is updated, as opposed to overwriting the row, i. ID of the transaction that created the version of the row. Both the old as well as the new versions of the row are stored and maintained, though the old versions are moved out of the database into a system database identified as Tempdb. When a row is in the process of being updated, any other requests are not blocked (unlike locking) but are executed on the older version of the row. If the other request is an update statement, it will result in two different versions of the rows. The query is expressed using a variant of SQL called T- SQL, a dialect Microsoft SQL Server shares with Sybase SQL Server due to its legacy. The query declaratively specifies what is to be retrieved. It is processed by the query processor, which figures out the sequence of steps that will be necessary to retrieve the requested data. The sequence of actions necessary to execute a query is called a query plan. There might be multiple ways to process the same query. For example, for a query that contains a join statement and a select statement, executing join on both the tables and then executing select on the results would give the same result as selecting from each table and then executing the join, but result in different execution plans. In such case, SQL Server chooses the plan that is expected to yield the results in the shortest possible time. This is called query optimization and is performed by the query processor itself. Given a query, then the query optimizer looks at the database schema, the database statistics and the system load at that time. It then decides which sequence to access the tables referred in the query, which sequence to execute the operations and what access method to be used to access the tables. For example, if the table has an associated index, whether the index should be used or not: if the index is on a column which is not unique for most of the columns (low . Finally, it decides whether to execute the query concurrently or not. While a concurrent execution is more costly in terms of total processor time, because the execution is actually split to different processors might mean it will execute faster. Once a query plan is generated for a query, it is temporarily cached. For further invocations of the same query, the cached plan is used. Unused plans are discarded after some time. Stored procedures are parameterized T- SQL queries, that are stored in the server itself (and not issued by the client application as is the case with general queries). Stored procedures can accept values sent by the client as input parameters, and send back results as output parameters. They can call defined functions, and other stored procedures, including the same stored procedure (up to a set number of times). They can be selectively provided access to. Unlike other queries, stored procedures have an associated name, which is used at runtime to resolve into the actual queries. Start SQL Server Management Studio. In the next step, you connect to SQL Server using the Object Explorer component of SSMS. If the Object Explorer pane is not visible, on the View menu, click Object Explorer. In the Object Explorer menu, click the Connect button, and then click Database Engine. The Connect to Server dialog box should appear. You can connect to one of three types of SQL Server. Each type has a slightly different format for the Server name box. Pick one of the following formats: -- A default instance of SQL Server: When you install SQL Server on a computer, you can specify that the instance of SQL Server will be a default (unnamed instance) or a named instance. If you are connecting to a default instance of SQL Server, insert the name of the computer. For example, if you are running SSMS on a computer named Accounting and you are connecting to a default instance of SQL Server installed on that computer, type Accounting in the Server name box.- - A named instance of SQL Server: During setup of SQL Server, you can specify a name for the instance; for example on a computer named Accounting, you could specify a named instance named Receivables. To connect to a named instance, in the Server name box, type the computer name backslash instance name; for example Accounting\Receivables.- - An Azure SQL Database: The format of the server name for SQL Database is SQL. If you have trouble determining your server name, visit the Azure portal for help creating a connection string.
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