I have a pretty long Oracle SQL query that needs to be compatible for Azure SQL. I am new to both database types. Here is query:
MERGE INTO studies
USING dual
ON (study_id = :study_id)
WHEN NOT MATCHED THEN
INSERT (study_id, study_date)
VALUES (:study_id, :study_date)
I am not sure USING dual would work. I read some solution saying that USING dual is not necessary in SQL Server.
I really appreciate if you can explain what this query means and how I can translate this for Azure SQL query.
This Oracle merge query has just a WHEN NOT MATCHED clause and no WHEN MATCHED, so basically that's insert and not exists:
insert into studies(study_id, study_date)
select x.*
from (values(#study_id, #study_date)) as x(study_id, study_date)
where not exists (select 1 from studies s1 where s1.study_id = x.study_id)
This is logically equivalent to the original Oracle query.
As for your original question: SQL Server does supports its own flavor or merge statement, whose syntax is different than Oracle. You would rewrite the Oracle merge as:
merge studies as s
using (values(#study_id, #study_date)) as x(study_id, study_date)
on (s.study_id = x.study_id)
when not matched
then insert (study_id, study_date) values(x.study_id, x.study_date)
I have a Linked Server to the AS400 here. I'm trying to pull data from a field, but it is pulling over a million records when I only need about 20k.
I have a list of IDs that I need, and I'm trying to figure out how to pass that list into the OpenQuery.
Here is my OpenQuery:
SELECT * FROM OPENQUERY(AS400, '
SELECT
IMITNO, IMITD1, IMITD2, IMMFNO, IMBMTP, IMDSCO
FROM AS400.APLUS2FLE.ITMST
WHERE IMDSCO != ''Y''
')
I want to add WHERE IMITNO IN (SELECT item_id FROM as400_item_scope) but the as400_item_scope table is on the SQL machine, not the AS400. I looked at several examples and I can pass in a single variable, but I don't understand how to pass in a list/query like this.
I'm using latest SSMS, but SQL Server Version is 2008
You can't as far as I know...
Two options..
Insert the results of SELECT item_id FROM as400_item_scope into a (temporary?) table on the IBM i and then reference that table in your openquery.
build a comma delimited string with from the results of SELECT item_id FROM as400_item_scope and include that in your openquery string.
Depending on how many records are returned, you might run into issues with statement size trying to use option #2. Db2 for IBM i supports SQL statement of up to 2,097,152 bytes...
We have a DB2 database in AS400. Added a linked server, all went well, however occasionally the table is locked, even when we doing some select queries. Thinking about table hint in SQL Server, does the linked server query (e.g. select * from ...) support table hint?
Doubtful, but I don't know for sure.
Are you using openquery() , or 4 part names?
A query using 4 part names like so:
select * from LNKSVRNAME.IBMINAME.MYSCHEMA.MYTABLE where somecolumn = '00335';
Pulls back all the rows from MYTABLE and does the WHERE filtering on MS SQL Server.
In contrast, using openquery() like so:
select * from openquery(LNKSVRNAME, 'select * from MYSCHEMA.MYTABLE where somecolumn = ''00335''');
Sends the query to the IBM i, and only the matching rows from MYTABLE are pulled back into MS SQL Server.
If the table is being locked exclusively, there's not much you can do. However, if you're running into row locks. You may want to look at the following DB2 for IBM i clauses
FOR READ ONLY
SKIP LOCKED DATA or USE CURRENTLY COMMITTED or WAIT FOR OUTCOME
So something like this:
select * from openquery(LNKSVRNAME, 'select * from MYSCHEMA.MYTABLE where somecolumn = ''00335'' FOR READ ONLY USE CURRENTLY COMMITTED');
Note If you are actually talking to an AS/400, FOR READ ONLY is all you'll have available. But if you're talking to a relatively recent IBM POWER System running a relatively recent version of IBM i, then the concurrent-access-resolution clauses I've shown should be available.
While in Management Studio, I am trying to run a query/do a join between two linked servers.
Is this a correct syntax using linked db servers:
select foo.id
from databaseserver1.db1.table1 foo,
databaseserver2.db1.table1 bar
where foo.name=bar.name
Basically, do you just preface the db server name to the db.table ?
The format should probably be:
<server>.<database>.<schema>.<table>
For example:
DatabaseServer1.db1.dbo.table1
Update: I know this is an old question and the answer I have is correct; however, I think any one else stumbling upon this should know a few things.
Namely, when querying against a linked server in a join situation the ENTIRE table from the linked server will likely be downloaded to the server the query is executing from in order to do the join operation. In the OP's case, both table1 from DB1 and table1 from DB2 will be transferred in their entirety to the server executing the query, presumably named DB3.
If you have large tables, this may result in an operation that takes a long time to execute. After all it is now constrained by network traffic speeds which is orders of magnitude slower than memory or even disk transfer speeds.
If possible, perform a single query against the remote server, without joining to a local table, to pull the data you need into a temp table. Then query off of that.
If that's not possible then you need to look at the various things that would cause SQL server to have to load the entire table locally. For example using GETDATE() or even certain joins. Others performance killers include not giving appropriate rights.
See http://thomaslarock.com/2013/05/top-3-performance-killers-for-linked-server-queries/ for some more info.
SELECT * FROM OPENQUERY([SERVER_NAME], 'SELECT * FROM DATABASE_NAME..TABLENAME')
This may help you.
For those having trouble with these other answers , try OPENQUERY
Example:
SELECT * FROM OPENQUERY([LinkedServer], 'select * from [DBName].[schema].[tablename]')
If you still find issue with <server>.<database>.<schema>.<table>
Enclose server name in []
You need to specify the schema/owner (dbo by default) as part of the reference. Also, it would be preferable to use the newer (ANSI-92) join style.
select foo.id
from databaseserver1.db1.dbo.table1 foo
inner join databaseserver2.db1.dbo.table1 bar
on foo.name = bar.name
select * from [Server].[database].[schema].[tablename]
This is the correct way to call.
Be sure to verify that the servers are linked before executing the query!
To check for linked servers call:
EXEC sys.sp_linkedservers
right click on a table and click script table as select
select name from drsql01.test.dbo.employee
drslq01 is servernmae --linked serer
test is database name
dbo is schema -default schema
employee is table name
I hope it helps to understand, how to execute query for linked server
Usually direct queries should not be used in case of linked server because it heavily use temp database of SQL server. At first step data is retrieved into temp DB then filtering occur. There are many threads about this. It is better to use open OPENQUERY because it passes SQL to the source linked server and then it return filtered results e.g.
SELECT *
FROM OPENQUERY(Linked_Server_Name , 'select * from TableName where ID = 500')
For what it's worth, I found the following syntax to work the best:
SELECT * FROM [LINKED_SERVER]...[TABLE]
I couldn't get the recommendations of others to work, using the database name. Additionally, this data source has no schema.
In sql-server(local) there are two ways to query data from a linked server(remote).
Distributed query (four part notation):
Might not work with all remote servers. If your remote server is MySQL then distributed query will not work.
Filters and joins might not work efficiently. If you have a simple query with WHERE clause, sql-server(local) might first fetch entire table from the remote server and then apply the WHERE clause locally. In case of large tables this is very inefficient since a lot of data will be moved from remote to local. However this is not always the case. If the local server has access to remote server's table statistics then it might be as efficient as using openquery More details
On the positive side T-SQL syntax will work.
SELECT * FROM [SERVER_NAME].[DATABASE_NAME].[SCHEMA_NAME].[TABLE_NAME]
OPENQUERY
This is basically a pass-through. The query is fully processed on the remote server thus will make use of index or any optimization on the remote server. Effectively reducing the amount of data transferred from the remote to local sql-server.
Minor drawback of this approach is that T-SQL syntax will not work if the remote server is anything other than sql-server.
SELECT * FROM OPENQUERY([SERVER_NAME], 'SELECT * FROM DATABASE_NAME.SCHEMA_NAME.TABLENAME')
Overall OPENQUERY seems like a much better option to use in majority of the cases.
I have done to find out the data type in the table at link_server using openquery and the results were successful.
SELECT * FROM OPENQUERY (LINKSERVERNAME, '
SELECT DATA_TYPE, COLUMN_NAME
FROM [DATABASENAME].INFORMATION_SCHEMA.COLUMNS
WHERE
TABLE_NAME =''TABLENAME''
')
Its work for me
Following Query is work best.
Try this Query:
SELECT * FROM OPENQUERY([LINKED_SERVER_NAME], 'SELECT * FROM [DATABASE_NAME].[SCHEMA].[TABLE_NAME]')
It Very helps to link MySQL to MS SQL
PostgreSQL:
You must provide a database name in the Data Source DSN.
Run Management Studio as Administrator
You must omit the DBName from the query:
SELECT * FROM OPENQUERY([LinkedServer], 'select * from schema."tablename"')
For MariaDB (and so probably MySQL), attempting to specify the schema using the three-dot syntax did not work, resulting in the error "invalid use of schema or catalog". The following solution worked:
In SSMS, go to Server Objects > Linked Servers > Providers > MSDASQL
Ensure that "Dynamic parameter", "Level zero only", and "Allow inprocess" are all checked
You can then query any schema and table using the following syntax:
SELECT TOP 10 *
FROM LinkedServerName...[SchemaName.TableName]
Source: SELECT * FROM MySQL Linked Server using SQL Server without OpenQuery
Have you tried adding " around the first name?
like:
select foo.id
from "databaseserver1".db1.table1 foo,
"databaseserver2".db1.table1 bar
where foo.name=bar.name
I have two Sql Servers (two distinct databases, (i.e. two machines)) with the same structure. Is there a way to do a SELECT * FROM (SELECT * FROM TableOnServerA Union SELECT * FROM TableOnServerB)?
Thanks
Yes, just set them up as linked servers and then fully qualify the names in the form of LinkName.DatabaseName.SchemaName(dbo).TableName
SELECT * FROM serverA.database.owner.TableName
Union
SELECT * FROM serverB.database.owner.Tablename
assuming that they are setup as linked server, use books online and go to "linked"
You could create a Linked Server or use OPENROWSET to connect to other SQL database.
You can run a query relating two different machines adding one machine via the sp_addlinkedserver stored procedure. You run it in the database server instance where you will want to execute the query (or on both if you want to execute the query in any server), like this
use master
go
exec sp_addlinkedserver
#server='AnotherServer',
#provider='SQL Server'
The you can run
select * from AnotherServer.database.dbo.table t1
join database.dbo.table t2 on (t1.id = t2.id)
Incidentally if they are on two different servers and you are sure the data is not duplicated use union all, it will be much faster. Also never use select *,specify the field names. Other wise it will break if someone adds a column to A but not to B (or rearranges teh columns in B but not A) I would also add a column indicating which of the two servers the data came from, especially if they might have the same id number but attached to different data (which can happen if you are using autogenerated ids). This can save no end of trouble.