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);
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.
I am using SQL Server 2012 and have two tables with identical structure. I want to insert new records from table 1 to table 2 if they don't already exist in table 2.
If they already exist, I want to update all of the existing records in table 2.
There are some 30 columns in my tables and I want to update all of them.
Can someone please help with this? I had a look at various links posted over internet, but quite don't understand how my statement should look like.
It's really not that hard....
You need:
a source table (or query) to provide data
a target table to merge it into
a condition on which those two tables are checked
a statement what to do if a match (on that condition) is found
a statement what to do if NO match (on that condition) is found
So basically, it's something like:
-- this is your TARGET table - this is where the data goes into
MERGE dbo.SomeTable AS target
-- this is your SOURCE table where the data comes from
USING dbo.AnotherTable AS source
-- this is the CONDITION they have to "meet" on
ON (target.SomeColumn = source.AnotherColumn)
-- if there's a match, so if that row already exists in the target table,
-- then just UPDATE whatever columns in the existing row you want to update
WHEN MATCHED THEN
UPDATE SET Name = source.Name,
OtherCol = source.SomeCol
-- if there's NO match, that is the row in the SOURCE does *NOT* exist in the TARGET yet,
-- then typically INSERT the new row with whichever columns you're interested in
WHEN NOT MATCHED THEN
INSERT (Col1, Col2, ...., ColN)
VALUES (source.Val1, source.Val2, ...., source.ValN);
I use SQL Server 2014.
In my procedure, I have a MERGE statement and I have a question about it.
My MERGE statement has simple following structure:
MERGE dbo.T1 AS tgt
USING (SELECT ...) AS src ON ...
WHEN MATCHED THEN
UPDATE ...
WHEN NOT MATCHED THEN
INSERT ...
OUTPUT inserted.MyColumn
INTO #NewTable (MyColumnValue);
Just like how it populates a table for all inserts, I also need it to populate another table for all updates too.
Is is possible, and if yes then would you please let me know how?
No, it's not possible to direct the results to two tables. See this question.
You can make the table wider and output both the inserted and deleted columns on the same row:
MERGE dbo.T1 AS tgt
USING (SELECT ...) AS src ON ...
WHEN MATCHED THEN
UPDATE ...
WHEN NOT MATCHED THEN
INSERT ...
OUTPUT $action, inserted.col1, inserted.col2, deleted.col1, deleted.col2
INTO #NewTable (action, inserted_col1, inserted_col2, deleted_col1, deleted_col2);
Then you can split #NewTable however you want.
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
I am trying to figure out which i need to use here: deleted, inserted or updated.
basically.
I need to write some data to the history table, when the main table is updated, and only if the status changes from something to either pending or active.
This is what I have now:
ALTER TRIGGER [dbo].[trg_SourceHistory] ON [dbo].[tblSource]
FOR UPDATE AS
DECLARE #statusOldValue char(1)
DECLARE #statusNewValue char(1)
SELECT #statusOldValue = statusCode FROM deleted
SELECT #statusNewValue= statusCode FROM updated
IF (#statusOldValue <> #statusNewValue) AND
(#statusOldValue = 'P' or #statusOldValue = 'A')
BEGIN TRY
INSERT * INTO tblHistoryTable)
select * from [DELETED]
so I want the new data to stay in the main table, the the history table to be updated with what is being overwritten... right now it just copies the same info over. so after update, both my tables have the same data.
There are only the Inserted and Deleted pseudo tables - there's no Updated.
For an UPDATE, Inserted contains the new values (after the update) while Deleted contains the old values before the update.
Also be aware that the triggers is fired once per batch - not once for each row. So both pseudo tables will potentially contain multiple rows! Don't just assume a single row and assign this to a variable - this
SELECT #statusOldValue = statusCode FROM deleted
SELECT #statusNewValue= statusCode FROM updated
will fail if you have multiple rows ! You need to write your triggers in such a fashion that they work with multiple rows in Inserted and Deleted !
Update: yes - there IS a much better way to write this:
ALTER TRIGGER [dbo].[trg_SourceHistory] ON [dbo].[tblSource]
FOR UPDATE
AS
INSERT INTO dbo.tblHistoryTable(Col1, Col2, Col3, ...., ColN)
SELECT Col1, COl2, Col3, ..... ColN
FROM Deleted d
INNER JOIN Inserted i ON i.PrimaryKey = d.PrimaryKey
WHERE i.statusCode <> d.statusCode
AND d.statusCode IN ('A', 'P')
Basically:
explicitly specify the columns you want to insert - both in the INSERT statement as well as the SELECT statement retrieving the data to insert - to avoid any nasty surprises
create an INNER JOIN between Inserted and Deleted pseudo-tables to get all rows that were updated
specify all other conditions (different status codes etc.) in the WHERE clause of the SELECT
This solution works for batches of rows being updated - it won't fail on a multi-row update....
You need to use both the inserted and deleted tables together to check for records that:
1. Already existed (to check it's not an insert)
2. Still exists (to check it's not a delete)
3. The Status field changed
You also need to make sure you do that in a set based approach, as per marc_s's answer, triggers are not single record processes.
INSERT INTO
tblHistoryTable
SELECT
deleted.*
FROM
inserted
INNER JOIN
deleted
ON inserted.PrimaryKey = deleted.PrimaryKey
WHERE
inserted.StatusCode <> deleted.StatusCode
AND (inserted.StatusCode = 'P' OR inserted.StatusCode = 'A')
inserted = the new values
deleted = the old values
There is no updated table, you are looking for inserted.