A SQL statement typically used to `UPDATE` records when they exist and `INSERT` them when they do not.

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Does MERGE updates when not needed?

In SQL Server 2012, Does a merge statement like this : WHEN MATCHED THEN update SET A.len = B.len updates a row even if A.len equals to B.len ? Or does the SQL SERVER knows to ignore this ...
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Once in a while synchronization of the independently updated mysql databases problem

I have a production database and a test database running on MySQL with MyISAM and InnoDB tables, which are updated independently. The Production database is updated by system and sometimes by a user. ...
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RETURNING syntax with multiple columns

Again, another question related to the answer of the one there: Insert with OUTPUT correlated to sub query table So I ended up with this query, written for SQL Server: CREATE TABLE tempIDs ( ...
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How to merge rows based on how much data they have?

I am cleaning data and I formed a table something like this: file | product | color | product_id --------------------------------------------- one.csv pipe blue null ...
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What overhead is there if I MERGE row by row?

I have a target table of about 2000 rows and I want to be able to MERGE (with HOLDLOCK) about 5-10 rows at a time into the target table. The target table doesn't get used heavily, with only 1-2 users ...
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Merge Similar Schema from one MySQL DB to Another

I have two databases (db1 and db2). db2 has all tables from db1 but not necessarily the same columns. I want to move any missing columns in db2 from tables in db1 but keep the rest unchanged. ...
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Merging Large Database Tables Quickly

So I found this other post; Merge multiple tables in a database And that's the general idea, but at an insanely large scale. Anyway -- Over the years, Our site has adapted and three different things ...
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Oracle merge query vs correlated update

I have a query which updates a table with data from another table. The current query is written as a correlated update with an exists clause to remove unnecessary rows. The problem is since both of ...