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)
In my SQL Server 2012 database, I have a linked server reference to a second SQL Server database that I need to pull records from and update accordingly.
I have the following update statement that I am trying to run:
UPDATE
Linked_Tbl
SET
Transferred = 1
FROM
MyLinkedServer.dbo.MyTable Linked_Tbl
JOIN
MyTable Local_Tbl ON Local_Tbl.LinkedId = Linked_Tbl.Id
JOIN
MyOtherTable Local_Tbl2 ON Local_Tbl.LocalId = Local_Tbl2.LocalId
Which I had to stop after an hour of running as it was still executing.
I've read online and found solutions stating that the best solution is to create a stored procedure on the Linked Server itself to execute the update statement rather than run it over the wire.
The problems I have are:
I don't have the ability to create any procedures on the other server.
Even if I could create that procedure, I would need to pass through all the Ids to the stored procedure for the update and I'm not sure how to do that efficiently with thousands of Ids (this, obviously, is the smaller of the issues, though since I can't create that procedure in the first place).
I'm hoping there are other solutions people may have managed to come up with given that it's often the case you don't have permissions to make changes to a different server.
Any ideas??
I am not sure, whether it can give more performance, you an try:
UPDATE
Linked_Tbl
SET
Transferred = 1
FROM OPENDATASOURCE([MyLinkedServer],'select Id, LocalId,Transferred from remotedb.dbo.MyTable') AS Linked_Tbl
JOIN MyTable Local_Tbl
ON Local_Tbl.LinkedId = Linked_Tbl.Id
JOIN MyOtherTable Local_Tbl2
ON Local_Tbl.LocalId = Local_Tbl2.LocalId
I need to join a Teradata table with about 0.5 billion records and a local table with about 10,000 records. I have it working in MS Access and it takes about 15 minutes to run. I would prefer to do it in SQL Server but can't even get a join with 1 record in the local SQL table to work.
Why is MS Access able to do this, albeit slowly, whereas SQL Server chokes? What is MS Access doing differently from SQL Server?
The SQL Server query with a join that fails:
SELECT a.trk, a.wgt
FROM openquery(TERADATA, 'SELECT trk, wgt
FROM SHIPMENT_DB.pkg') a
INNER JOIN (Local_Tbl) b ON a.trk = b.Tracking_Number
A simple SQL Server query without a join that works:
SELECT *
FROM openquery(TERADATA,'SELECT trk, wgt
FROM SHIPMENT_DB.pkg
WHERE trk = ''773423067500''')
Not the answer, but I had a similar issue using OPENDATASOURCE. Performance was terrible, the query took hours to run.
The solution was to ensure all colmns involved in the WHERE clause had mathcing datatypes. In my case the remote column was INT but in the query it was being passed as a varchar: ...'WHERE remote_table.ID = ''4'''...
Once I changed all values to the appropriate datatypes the query took seconds to run.
Look at the Execution Plan in SQL Server. Since it knows very little about the dataset that is going to come back from Teradata, it is making some has assumptions.
Swapping the order of the tables in the join will help. Using an explicit INNER HASH JOIN may help (once you've switched the order).
I have one table in SQL server and 5 tables in Teradata.I want to join those 5 table in teradata with sql server table and store result in Teradata table.
I have sql server name but i dont know how to simultaneously run a query both on sql server and teradata.
i want to do this:
sql server table query
Select distinct store
from store_Desc
teradata tables:
select cmp_id,state,sde
from xyz
where store in (
select distinct store
from sql server table)
You can create a table (or a volatile table if you do not have write privileges) to do this. Export result from SQL Server as text or into the language of your choice.
CREATE VOLATILE TABLE store_table (
column_1 datatype_1,
column_2 datatype_2,
...
column_n datatype_n);
You may need to add ON COMMIT PRESERVE ROWS before the ; to the above depending on your transaction settings.
From a language you can loop the below or do an execute many.
INSERT INTO store_table VALUES(value_1, value_2, ..., value_n);
Or you can use the import from text using Teradata SQL Assistant by going to File and selecting Import. Then execute the below and navigate to your file.
INSERT INTO store_table VALUES(?, ?, ..., n);
Once you have inserted your data you can query it by simply referencing the table name.
SELECT cmp_id,state,sde
FROM xyz
WHERE store IN(
SELECT store
FROM store_table)
The DISTINCT function is most easily done on export from SQL Server to minimize the rows you need to upload.
EDIT:
If you are doing this many times you can do this with a script, here is a very simple example in Python:
import pyodbc
con_ss = pyodbc.connect('sql_server_odbc_connection_string...')
crs_ss = con_ss.cursor()
con_td = pyodbc.connect('teradata_odbc_connection_string...')
crs_td = con_td.cursor()
# pull data for sql server
data_ss = crs_ss.execute('''
SELECT distinct store AS store
from store_Desc
''').fetchall()
# create table in teradata
crs_td.execute('''
CREATE VOLATILE TABLE store_table (
store DEC(4, 0)
) PRIMARY INDEX (store)
ON COMMIT PRESERVE ROWS;''')
con_td.commit()
# insert values; you can also use an execute many, but this is easier to read...
for row in data_ss:
crs_td.execute('''INSERT INTO store_table VALUES(?)''', row)
con_td.commit()
# get final data
data_td = crs_td.execute('''SELECT cmp_id,state,sde
FROM xyz
WHERE store IN(
SELECT store
FROM store_table);''').fetchall()
# from here write to file or whatever you would like.
Is fetching data from the Sql Server through ODBC an option?
The best option may be to use Teradata Parallel Transporter (TPT) to fetch data from SQL Server using its ODBC operator (as a producer) combined with Load or Update operator as the consumer to insert it into an intermediate table on Teradata. You must then perform rest of the operations on Teradata. For the rest of the operations, you can use BTEQ/SQLA to store the results in the final Teradata table. You can also put the same SQL in TPT's DDL operator instead of BTEQ/SQLA and get it done in a single job script.
To allow use of tables residing on separate DB environments (in your case SQL-Server and Teradata) in a single select statement, Teradata has recently released Teradata Query Grid. But I'm not sure about exact level of support for SQL-Server and it will involve licensing hassle and quite a learning curve to do this simple job.
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