CODEWITHSUNDEEP
t-sqlstored-proceduresconstraints
Tomasz Kapłoński
Tomasz Kapłoński

Reputation: 1378

insert ignoring duplicates using TSQL

I have a table with unique constraint on 2 columns:

CREATE TABLE MIGRATION_DICTIONARIES.dbo._TableQueue_ (
    Id INT IDENTITY PRIMARY KEY,
    TableName VARCHAR(250),
    TableFrom VARCHAR(250),
    KeyName VARCHAR(250),
    Processed INT DEFAULT 0,

    CONSTRAINT [UQ_codes] UNIQUE NONCLUSTERED
    (
        TableName, TableFrom
    )
)

In a procedure I am trying to implement I need to insert a bunch of records using INSERT INTO (...) SELECT. Now, how can I make sure that any rows that duplicate the constraint will be ignored but all the other rows given by the select statement still saved?

The query with insert:

INSERT INTO MIGRATION_DICTIONARIES.dbo._TableQueue_ (TableName, TableFrom, KeyName)
SELECT 'some_table_name', t.name as TableWithForeignKey, c.name as ForeignKeyColumn 
from sys.foreign_key_columns as fk
inner join sys.tables as t on fk.parent_object_id = t.object_id
inner join sys.columns as c on fk.parent_object_id = c.object_id and fk.parent_column_id = c.column_id
where fk.referenced_object_id = (select object_id from sys.tables where name = 'some_table_name')

[EDIT] I ended with following query:

MERGE MIGRATION_DICTIONARIES.dbo._TableQueue_ AS T
USING (
    SELECT 'SomeTable' as TableFrom, t.name as TableWithForeignKey, c.name as ForeignKeyColumn 
    from sys.foreign_key_columns as fk
    inner join sys.tables as t on fk.parent_object_id = t.object_id
    inner join sys.columns as c on fk.parent_object_id = c.object_id and fk.parent_column_id = c.column_id
    where fk.referenced_object_id = (select object_id from sys.tables where name = 'SomeTable')
) AS S
ON (T.TableName = S.TableWithForeignKey AND T.TableFrom = S.TableFrom)
WHEN NOT MATCHED BY TARGET THEN
    INSERT (TableName, TableFrom, KeyName)
    VALUES (S.TableFrom, S.TableWithForeignKey, S.ForeignKeyColumn);

But when I run it I still get constraint error:

Violation of UNIQUE KEY constraint 'UQ_codes'. Cannot insert duplicate key in object 'dbo._TableQueue_'. The duplicate key value is (UP_Opiekun, UP_Uczen).
The statement has been terminated.

What do I do wrong?

Upvotes: 0

Views: 1410

Answers (1)

gbn
gbn

Reputation: 432261

For SQL Server 2008 you can use the MERGE statement with only a "WHEN NOT MATCHED BY TARGET" clause to INSERT. Don't use a "WHEN MATCHED" clause

More generally, you can also use 

INSERT dbo._TableQueue_
   (....)
SELECT
   ...
FROM
   SOurce S
WHERE
   NOT EXISTS (SELECT *
      FROM dbo._TableQueue_ T
      WHERE
         S.TableName = T.TableName AND S.TableFrom = T.TableFrom
      )

After comment:

MERGE INTO dbo._TableQueue_ T
USING Source S
       ON S.TableName = T.TableName AND S.TableFrom = T.TableFrom
WHEN NOT MATCHED BY TARGET THEN
   INSERT (...)
   VALUES (S.x. S.y, ...);

Upvotes: 2

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