Selecting data from two different servers in SQL Server

What you are looking for are Linked Servers. You can get to them in SSMS from the following location in the tree of the Object Explorer:

Server Objects-->Linked Servers

or you can use sp_addlinkedserver.

You only have to set up one. Once you have that, you can call a table on the other server like so:

select
    *
from
    LocalTable,
    [OtherServerName].[OtherDB].[dbo].[OtherTable]

Note that the owner isn't always dbo, so make sure to replace it with whatever schema you use.

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You can do it using Linked Server.

Typically linked servers are configured to enable the Database Engine to execute a Transact-SQL statement that includes tables in another instance of SQL Server, or another database product such as Oracle. Many types OLE DB data sources can be configured as linked servers, including Microsoft Access and Excel.

Linked servers offer the following advantages:

The ability to access data from outside of SQL Server.

The ability to issue distributed queries, updates, commands, and transactions on heterogeneous data sources across the enterprise.

The ability to address diverse data sources similarly.

Read more about Linked Servers.

Follow these steps to create a Linked Server:

Server Objects -> Linked Servers -> New Linked Server Provide Remote Server Name. Select Remote Server Type (SQL Server or Other). Select Security -> Be made using this security context and provide login and password of remote server. Click OK and you are done !!

Here is a simple tutorial for creating a linked server.

OR

You can add linked server using query.

Syntax:

sp_addlinkedserver [ @server= ] 'server' [ , [ @srvproduct= ] 'product_name' ] 
     [ , [ @provider= ] 'provider_name' ]
     [ , [ @datasrc= ] 'data_source' ] 
     [ , [ @location= ] 'location' ] 
     [ , [ @provstr= ] 'provider_string' ] 
     [ , [ @catalog= ] 'catalog' ] 

Read more about sp_addlinkedserver.

You have to create linked server only once. After creating linked server, we can query it as follows:

select * from LinkedServerName.DatabaseName.OwnerName.TableName

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SELECT
        *
FROM
        [SERVER2NAME].[THEDB].[THEOWNER].[THETABLE]

You can also look at using Linked Servers. Linked servers can be other types of data sources too such as DB2 platforms. This is one method for trying to access DB2 from a SQL Server TSQL or Sproc call...

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Querying across 2 different databases is a distributed query. Here is a list of some techniques plus the pros and cons:

Linked servers: Provide access to a wider variety of data sources than SQL Server replication provides Linked servers: Connect with data sources that replication does not support or which require ad hoc access Linked servers: Perform better than OPENDATASOURCE or OPENROWSET OPENDATASOURCE and OPENROWSET functions: Convenient for retrieving data from data sources on an ad hoc basis. OPENROWSET has BULK facilities as well that may/may not require a format file which might be fiddley OPENQUERY: Doesn't support variables All are T-SQL solutions. Relatively easy to implement and set up All are dependent on connection between source and destionation which might affect performance and scalability

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These are all fine answers, but this one is missing and it has it's own powerful uses. Possibly it doesn't fit what the OP wanted, but the question was vague and I feel others may find their way here. Basically you can use 1 window to simultaneously run a query against multiple servers, here's how:

In SSMS open Registered Servers and create a New Server Group under Local Server Groups.

Under this group create New Server Registration for each server you wish to query. If the DB names are different ensure to set a default for each in the properties.

Now go back to the Group you created in the first step, right click and select New Query. A new query window will open and any query you run will be executed on each server in the group. The results are presented in a single data set with an extra column name indicating which server the record came from. If you use the status bar you will note the server name is replaced with multiple.

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try this:

SELECT * FROM OPENROWSET('SQLNCLI', 'Server=YOUR SERVER;Trusted_Connection=yes;','SELECT * FROM Table1') AS a
UNION
SELECT * FROM OPENROWSET('SQLNCLI', 'Server=ANOTHER SERVER;Trusted_Connection=yes;','SELECT * FROM Table1') AS a

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I had the same issue to connect an SQL_server 2008 to an SQL_server 2016 hosted in a remote server. Other answers didn't worked for me straightforward. I write my tweaked solution here as I think it may be useful for someone else.

An extended answer for remote IP db connections:

Step 1: link servers

EXEC sp_addlinkedserver @server='SRV_NAME',
   @srvproduct=N'',
   @provider=N'SQLNCLI',   
   @datasrc=N'aaa.bbb.ccc.ddd';
   
EXEC sp_addlinkedsrvlogin 'SRV_NAME', 'false', NULL, 'your_remote_db_login_user', 'your_remote_db_login_password'

...where SRV_NAME is an invented name. We will use it to refer to the remote server from our queries. aaa.bbb.ccc.ddd is the ip address of the remote server hosting your SQLserver DB.

Step 2: Run your queries For instance:

SELECT * FROM [SRV_NAME].your_remote_db_name.dbo.your_table

...and that's it!

Syntax details: sp_addlinkedserver and sp_addlinkedsrvlogin

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Server 2008:

When in SSMS connected to server1.DB1 and try:

SELECT  * FROM
[server2].[DB2].[dbo].[table1]

as others noted, if it doesn't work it's because the server isn't linked.

I get the error:

Could not find server DB2 in sys.servers. Verify that the correct server name was specified. If necessary, execute stored procedure sp_addlinkedserver to add the server to sys.servers.

To add the server:

reference: To add server using sp_addlinkedserver Link: [1]: To add server using sp_addlinkedserver

To see what is in your sys.servers just query it:

SELECT * FROM [sys].[servers]

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Simplified solution for adding linked servers

First server

EXEC sp_addlinkedserver @server='ip,port\instancename'

Second Login

EXEC sp_addlinkedsrvlogin 'ip,port\instancename', 'false', NULL, 'remote_db_loginname', 'remote_db_pass'

Execute queries from linked to local db

INSERT INTO Tbl (Col1, Col2, Col3)
SELECT Col1, Col2, Col3
FROM [ip,port\instancename].[linkedDBName].[linkedTblSchema].[linkedTblName]

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Created a Linked Server definition in one server to the other (you need SA to do this), then just reference them with 4-part naming (see BOL).

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 select * 
 from [ServerName(IP)].[DatabaseName].[dbo].[TableName]

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As @Super9 told about OPENDATASOURCE using SQL Server Authentication with data provider SQLOLEDB . I am just posting here a code snippet for one table is in the current sever database where the code is running and another in other server '192.166.41.123'

SELECT top 2 * from dbo.tblHamdoonSoft  tbl1 inner JOIN  
OpenDataSource('SQLOLEDB','Data Source=192.166.41.123;User ID=sa;Password=hamdoonsoft')
.[TestDatabase].[dbo].[tblHamdoonSoft1] tbl2 on tbl1.id = tbl2.id

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I know this is an old question but I use synonyms. Supposedly the query is executed within database server A, and looks for a table in a database server B that does not exist on server A. Add then a synonym on A database that calls your table from server B. Your query doesn't have to include any schemas, or different database names, just call the table name per usual and it will work.

There's no need to link servers as synonyms per say are sort of linking.

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sp_addlinkedserver('servername')

so its should go like this -

select * from table1
unionall
select * from [server1].[database].[dbo].[table1]

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Server Objects---> linked server ---> new linked server

In linked server write server name or IP address for other server and choose SQL Server In Security select (be made using this security context ) Write login and password for other server

Now connected then use

Select * from [server name or ip addresses ].databasename.dbo.tblname

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