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C1 compressor free download tutorial6/17/2023 If this is tried, the Database Engine displays an error message. The Database Engine doesn't allow creating a unique index on columns that already include duplicate values, whether or not IGNORE_DUP_KEY is set to ON. A clustered index on a view must be unique. A unique index is one in which no two rows are permitted to have the same index key value. Arguments UNIQUEĬreates a unique index on a table or view. To view Transact-SQL syntax for SQL Server 2014 and earlier, see Previous versions documentation. Syntax for Azure Synapse Analytics and Parallel Data WarehouseĬREATE CLUSTERED COLUMNSTORE INDEX index_name Use the syntax structure specified in instead. The backward compatible relational index syntax structure will be removed in a future version of SQL Server.Īvoid using this syntax structure in new development work, and plan to modify applications that currently use the feature. Transact-SQL syntax conventions Syntax Syntax for SQL Server, Azure SQL Database, Azure SQL Managed Instance CREATE INDEX index_name For more information, see Columnstore Indexes - Data Warehouse. Starting with SQL Server 2016 (13.x) and SQL Database, you can use a nonclustered index on a columnstore index to improve data warehousing query performance. Any examples referencing unique constraints are only applicable to SQL Server and SQL Database.įor information on index design guidelines, refer to the SQL Server Index Design Guide.Ĭreate a nonclustered index on a table or view CREATE INDEX index1 ON schema1.table1 (column1) Ĭreate a clustered index on a table and use a 3-part name for the table CREATE CLUSTERED INDEX index1 ON 1 (column1) Ĭreate a nonclustered index with a unique constraint and specify the sort order CREATE UNIQUE INDEX index1 ON schema1.table1 (column1 DESC, column2 ASC, column3 DESC) For more information, see the SQL Server and Azure SQL index architecture and design guide.Īzure Synapse Analytics and Analytics Platform System (PDW) currently don't support unique constraints. This does not apply to columnstore indexes or in-memory data stores. In rowstore indexes, SQL Server implements a B+ tree. SQL Server documentation uses the term B-tree generally in reference to indexes.
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