This is my query
SELECT PageVisit_ID,TargetSite_ID FROM [A].Datawarehouse.mi.ctb_PageEvent WITH (NOLOCK)
EXCEPT
SELECT PageVisit_ID ,TargetSite_ID FROM [B].Datawarehouse.mi.ctb_PageEvent WITH (NOLOCK)
these two tables from two servers. I need to update targetsite_id in [A].Datawarehouse.mi.ctb_PageEvent records from [B].Datawarehouse.mi.ctb_PageEvent
only matched with above query results.
Try this
DECLARE #SummaryOfChanges TABLE(Change VARCHAR(20));
MERGE INTO [A].Datawarehouse.mi.ctb_PageEvent AS Target
USING ( SELECT PageVisit_ID ,TargetSite_ID FROM [B].Datawarehouse.mi.ctb_PageEvent WITH (NOLOCK)) AS SOURCE
ON Target.TargetSite_ID = Source.TargetSite_ID
WHEN MATCHED THEN
//UPDATE OR do nothing
WHEN NOT MATCHED BY TARGET THEN
//INSERT
OUTPUT $action INTO #SummaryOfChanges;
Please refer to SQL SERVER – Merge Operations – Insert, Update, Delete in Single Execution. my solution just gives a basic idea on how to do this. It might not work 100% initially. Just tweak it once you understand the logic
Related
I have a query that has as the output the following table (2 columns). What it means, is that I'm going to use the result to wrap it inside a merge into statement.
INSERT_COLUMNS UPDATE_COLUMNS
BANK_NAME target.BANK_NAME = source.BANKNAME
What I'm talking about is this:
with sql_prepare_merge as (
SELECT *
FROM another_table
),
MERGE INTO bank_raw AS target
USING bank AS source
ON source.id = target.id
WHEN MATCHED THEN
UPDATE SET (select update_columns from sql_prepare_merge)
WHEN NOT MATCHED THEN
INSERT (select insert_columns from sql_prepare_merge)
VALUES (source.id, (select insert_columns from sql_prepare_merge));
Keep in mind that the "sql_prepare_merge" is the name from the CTE where I'm getting the table I shared with you - and it has much more code in it, but they don't help here. So, I'm planning to take the text resulting from the subquery and insert it inside the merge statement.
So far, the error I'm getting is: syntax error line 19 at position 4 unexpected 'WHEN'.. By the way, this is inside Snowflake.
Unfortunately this is not possible as per my understanding of the docs: https://docs.snowflake.com/en/sql-reference/sql/merge.html#notmatchedclause-for-inserts
In the non matched clause for inserts you can specify only such values/expressions, refer to the source relations. This means you somehow need to adjust your source part itself (e.g. by joining the initial source with another_table). If this is not possible, you would need to go for separate INSERT and UPDATE statements.
Assume a table structure of MyTable(MyTableId NVARCHAR(MAX) PRIMARY KEY, NumberOfInserts INTEGER).
I often need to either update i.e. increment a counter of an existing record, or insert a new record if it doesn't exist with a value of 0 for NumberOfInserts.
Essentially:
IF (MyTableId exists)
run UPDATE command
ELSE
run INSERT command
My concern is losing data due to race conditions, etc.
What's the safest way to write this?
I need it to be 100% accurate if possible, and willing to sacrifice speed where necessary.
MERGE statement can perform both UPDATE and INSERT (and DELETE if needed).
Even though it is a single atomic statement, it is important to use HOLDLOCK query hint to prevent race condition. There is a blog post “UPSERT” Race Condition With MERGE by Dan Guzman where he explains in great details how it works and provides a test script to verify it.
The query itself is straight-forward:
DECLARE #NewKey NVARCHAR(MAX) = ...;
MERGE INTO dbo.MyTable WITH (HOLDLOCK) AS Dst
USING
(
SELECT #NewKey AS NewKey
) AS Src
ON Src.NewKey = Dst.[Key]
WHEN MATCHED THEN
UPDATE
SET NumberOfInserts = NumberOfInserts + 1
WHEN NOT MATCHED THEN
INSERT
(
[Key]
,NumberOfInserts
)
VALUES
(
#NewKey
,0
);
Of course, you can also use explicit two-step approach with a separate check if a row exists and separate UPDATE and INSERT statements. Just make sure to wrap them all in a transaction with appropriate table locking hints.
See Conditional INSERT/UPDATE Race Condition by Dan Guzman for details.
I'm having trouble getting this compound insert to work in my MERGE statement between two tables (Ignore the when match condition, I know its bad practice). The issue I'm having is getting the ServerId field in the target table to fill. The Team field is filling fine but all of the rows have a null value for ServerId. I can't find an example online for this so I'm hoping someone can help. I don't seem to have any syntactical errors and I know the column 'ServerName' in the Source table is filled for all rows.
MERGE ApplicationTeams AS Target
USING TempApplicationTeams AS Source
ON (Target.ServerId = (SELECT ID from Servers WHERE Name='Source.ServerName') AND Target.Team = Source.Team)
WHEN MATCHED THEN
UPDATE SET Target.Team = Target.Team
WHEN NOT MATCHED BY TARGET THEN
INSERT (ServerId, Team) VALUES((SELECT ID from Servers WHERE Name='Source.ServerName'), Source.Team)
WHEN NOT MATCHED BY SOURCE THEN
DELETE
;
Thanks.
I think you should remove the single quoutes on the where clausule.
You wrote:
(SELECT ID from Servers WHERE Name='Source.ServerName')
But I think you should write this:
(SELECT ID from Servers WHERE Name=Source.ServerName)
And make sure the select id returns only one row otherwise the statement will fail
I hope it will be usefully
I Know that OUTPUT Clause can be used in INSERT, UPDATE, DELETE, or MERGE statement. The results of an OUTPUT clause in a INSERT, UPDATE, DELETE, or MERGE statements can be stored into a target table.
But, when i run this query
select * from <Tablename> output
I didn't get any error. The query executed as like select * from tablename with out any error and with same no. of rows
So what is the exact use of output clause in select statement. If any then how it can be used?
I searched for the answer but i couldn't find a answer!!
The query in your question is in the same category of errors as the following (that I have also seen on this site)
SELECT *
FROM T1 NOLOCK
SELECT *
FROM T1
LOOP JOIN T2
ON X = Y
The first one just ends up aliasing T1 AS NOLOCK. The correct syntax for the hint would be (NOLOCK) or ideally WITH(NOLOCK).
The second one aliases T1 AS LOOP. To request a nested loops join the syntax would need to be INNER LOOP JOIN
Similarly in your question it just ends up applying the table alias of OUTPUT to your table.
None of OUTPUT, LOOP, NOLOCK are actually reversed keywords in TSQL so it is valid to use them as a table alias without needing to quote them, e.g. in square brackets.
OUTPUT clause return information about the rows affected by a statement. OUTPUT Clause is used along with INSERT, UPDATE, DELETE, or MERGE statements as you mentioned. The reason it is used is because these statements themselves just return the number of rows effected not the rows effected. Thus the usage of OUTPUT with INSERT, UPDATE, DELETE, or MERGE statements helps the user by returning actual rows effected.
SELECT statement itself returns the rows and SELECT doesn't effect any rows. Thus the usage of OUTPUT clause with SELECT is not required or supported. If you want to store the results of a SELECT statement into a target table use SELECT INTO or the standard INSERT along with the SELECT statement.
EDIT
I guess I misunderstood your question. AS #Martin Smith mentioned its is acting an alias in the SELECT statement you mentioned.
IF OBJECT_ID('tempdelete') IS NOT NULL DROP TABLE tempdelete
GO
IF OBJECT_ID('tempdb..#asd') IS NOT NULL DROP TABLE #asd
GO
CREATE TABLE tempdelete (
name NVARCHAR(100)
)
INSERT INTO tempdelete VALUES ('a'),('b'),('c')
--Creating empty temp table with the same columns as tempdelete
SELECT * INTO #asd FROM tempdelete WHERE 1 = 0
DELETE FROM tempdelete
OUTPUT deleted.* INTO #asd
SELECT * FROM #asd
This is how you can put all the deleted records in to a table. The problem with that is that you have to define the table with all the columns matching the table from which you are deleting. This is how i do it.
I’ve been tasked to synchronize 2 tables (both are identical). They have 60 columns each. Table A is the primary table that will be initially filled. I need to create a stored procedure (done) that will merge these 2 tables and populate both with the same exact data (Update, insert, delete) when called. How would I use the MERGE function in SQL to achieve this? I’ve looked at both the MSDN documentation and similar that’s on technet, but I’m pretty confused on getting started. Do I need to specify each field I need merged? Or is it a simple call I’m missing that will perform this action?
Here is a link to a simple example of the MERGE statement:
http://www.simple-talk.com/sql/learn-sql-server/the-merge-statement-in-sql-server-2008/
The basic syntax reads as:
MERGE table1
USING table2
ON table1.id = table2.id
WHEN MATCHED THEN
--Do an update here
WHEN NOT MATCHED BY TARGET THEN
--Do an insert here (or a delete)
;
You can also use WHEN NOT MATCHED BY SOURCE
Over 60 columns is a great number! When I need to sync 2 identical table I do:
;WITH tbl_to_synch as (
-- Prepare table to update,
Select *,chk = CHECKSUM(*) from [dbo].[tableA]
)
MERGE tbl_to_synch as [Target]
USING (Select *,chk = CHECKSUM(*) from [dbo].[tableB]) as [source]
ON [Target].key = [source].key
WHEN MATCHED AND [Target].chk <> [source].chk THEN
-- UPDATE ONLY row that is changed
UPDATE
SET
column01 = [source].[column01]
,column02 = [source].[column01]
-- ....
,column59 = [source].[column59]
,column60 = [source].[column59]
WHEN NOT MATCHED BY TARGET THEN
insert (column01, column02, ...,column59,column60)
values (column01, column02, ...,column59,column60)
WHEN NOT MATCHED BY SOURCE THEN DELETE
-- Show what is changed
OUTPUT $action, ISNULL(INSERTED.key,DELETED.key);