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POSQL Server ignore_dup_key on apparently ignored for merge statement
 

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  1. POSQL Server ignore_dup_key on apparently ignored for merge statement
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    <p>SQL Server 2008.</p> <p>I have few pieces of code working together and the effect is rather strange so I decided to share.</p> <p>I have a table with emails - for simplicity let as assume there are 2 columns: ID identity(1,1) int primary key email varchar(900)</p> <p>Also there is a unique key on email column with IGNORE_DUP_KEY = ON.</p> <p>On the other side of a problem is a merge statement:</p> <pre><code>merge into dbo.email using ( select distinct email t from #t ) p ON t = email when not matched by target then insert (email) values (t); </code></pre> <p>It is worth to note that #t is basically (for purpose of this query) a one column table with email varchar(500).</p> <p>What is surprising is that the query failed:</p> <p>"Violation of UNIQUE KEY constraint 'uq_email'. Cannot insert duplicate key in object dbo.email"</p> <p>However this works flawlessly:</p> <pre><code>insert into dbo.email (email) select email from #t </code></pre> <p>While I can obviously work around the problem (the insert statement is faster anyway so it is a way to go) I have no idea why the MERGE statement failed. Any ideas, anyone?</p> <p>EDIT: Full use case: Step 1:</p> <pre><code>create table #temp ( col1 varchar(500), col2 varchar(500), col3 varchar(500), col4 varchar(500), col5 varchar(500), email varchar(500), id int) </code></pre> <p>Step 2:</p> <p>#temp is populated from CSV file for many purposes</p> <p>Step 3:</p> <p>merge into dbo.email using ( select distinct email t from #temp ) p ON t = email when not matched by target then insert (email) values (t);</p> <p>Step 0 - CREATE script for dbo.email:</p> <pre><code>CREATE TABLE dbo.email ( id int identity(1,1) not null, email varchar(900) null, loaddate date default null, constraint [PK__email__1111] PRIMARY KEY CLUSTERED ( id asc ) WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON PRIMARY, CONSTRAINT [uq_email] UNIQUE NONCLUSTERED ( EMAIL asc ) ) WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = ON, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON PRIMARY ) ON PRIMARY </code></pre> <p>I can't make much more without giving you hunderds of gigabytes of data which is out of a question obviously.</p>
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    1. USnimdil
    1. USnimdil
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      1. POSQL Server ignore_dup_key on apparently ignored for merge statement
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      1. POSQL Server ignore_dup_key on apparently ignored for merge statement
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    1. COBased on the information you have given the statement should work correctly and not attempt to insert where matching rows already exist. Is there a trigger on the target `email` table?
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      1. USEd Harper
    2. CONo. There is really nothing else there. I'm also surprised that it failed as I see no reason (obviously). Maybe it is a bug in SQL Server. After all - as my prof used to say - it is just a software :-.
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      1. USnimdil
    3. COCan you post a complete example which demonstrates the problem? I've created a test based on the information you've provided and it works as expected.
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      1. USEd Harper
 

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