If you can't use identity values because of these restrictions, create a separate table holding a current value and manage access to the table and number assignment with your application. These restrictions are part of the design in order to improve performance, and because they're acceptable in many common situations. This can result in gaps when the subsequent identity values are generated. If a particular insert statement fails, or if the insert statement is rolled back then the consumed identity values are lost and aren't generated again. Reuse of values - For a given identity property with specific seed/increment, the identity values aren't reused by the engine. Using a sequence generator with the NOCACHE option can limit the gaps to transactions that are never committed. If gaps aren't acceptable, then the application should use its own mechanism to generate key values. This can result in gaps in the identity value upon insert. If values must be consecutive, then the transaction should use an exclusive lock on the table or use the SERIALIZABLE isolation level.Ĭonsecutive values after server restart or other failures - SQL Server might cache identity values for performance reasons and some of the assigned values can be lost during a database failure or server restart. For more information, see Using IDENTITY to create surrogate keys in a Synapse SQL pool.Ĭonsecutive values within a transaction - A transaction inserting multiple rows isn't guaranteed to get consecutive values for the rows because other concurrent inserts might occur on the table. To query more records radomly, increase the TOP value.Azure Synapse Analytics doesn't support PRIMARY KEY or UNIQUE constraint or UNIQUE index. The following example queries a random record from the Production.Product table using the NEWID() function. SELECT Query random data with the NEWID() function Then, the variable is assigned a value by using the SET statement. The following example declares a local variable called as a variable of uniqueidentifier data type. Using uniqueidentifier and variable assignment ,('Maison Dewey', 'Catherine Dewey', 'Rue Joseph-Bens 532', 'Bruxelles', NULL, ,('Ernst Handel', 'Roland Mendel', 'Kirchgasse 6', 'Graz', NULL, ,('Cactus Comidas para Ilevar', 'Patricio Simpson', 'Cerrito 333', 'Buenos Aires', NULL, ,('Wellington Importadora', 'Paula Parente', 'Rua do Mercado, 12', 'Resende', 'SP', ('Wartian Herkku', 'Pirkko Koskitalo', 'Torikatu 38', 'Oulu', NULL, PostalCode, CountryRegion, Telephone, Fax) (Company, ContactName, Address, City, StateProvince, Creating a table using NEWID for uniqueidentifier data type. In assigning the default value of NEWID(), each new and existing row has a unique value for the CustomerID column. The following example creates the cust table with a uniqueidentifier data type, and uses NEWID to fill the table with a default value. This number is shown only for illustration. The value returned by NEWID is different for each computer.
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