如果READ_COMMITTED_SNAPSHOT 数据库选项设置为 OFF(这是 SQL Server 和 Azure SQL托管实例中的默认设置),当前事务运行读取操作时,READ COMMITTED 隔离使用共享锁来防止其他事务修改行。 共享锁还会阻止语句在其他事务完成之前读取由这些事务修改的行。 两个实现都满足 READ COMMITTED 隔离的 ISO 定义。 SN...
column1, column2, ... column_n The columns that make up the unique constraint. Example Let's look at an example of how to add a unique constraint to an existing table in SQL Server using the ALTER TABLE statement. ALTER TABLE employees ADD CONSTRAINT employees_unique UNIQUE (employee_numbe...
Server. $tb.Create() #Create a unique, clustered, primary key index on the integer column. This is required for an XML index. #Define an Index object variable by providing the parent table and index name in the constructor. $cp = New-Object -TypeName Microsoft.SqlServer.M...
從SQL Server 2016 (13.x) 開始,您在資料行存放區索引上可以有一個或多個非叢集資料列存放區索引,而且可以針對基礎資料行存放區執行有效率的資料表搜尋。 其他選項也變得可用。 例如,您可以在資料列存放區資料表上使用 UNIQUE 條件約束,強制執行主索引鍵條件約束。 由於非唯一值將無法插入至資料列存放區資料表,...
CREATE INDEX index1 ON schema1.table1 (column1); Create a clustered index on a table and use a 3-part name for the table SQL Copy CREATE CLUSTERED INDEX index1 ON database1.schema1.table1 (column1); Create a nonclustered index with a unique constraint and specify the sort order...
在SQL Server 中,以使用者指定的格式,將資料檔匯入資料庫數據表或檢視。Transact-SQL 語法慣例語法syntaxsql 複製 BULK INSERT { database_name.schema_name.table_or_view_name | schema_name.table_or_view_name | table_or_view_name } FROM 'data_file' [ WITH ( [ [ , ] DATA_SOURCE = 'data_...
IGNORE_DUP_KEY can't be set to ON for indexes created on a view, non-unique indexes, XML indexes, spatial indexes, and filtered indexes.To view the IGNORE_DUP_KEY setting for an index, use the ignore_dup_key column in the sys.indexes catalog view....
Applies to: SQL Server 2008 (10.0.x) and later versions. Applies only to thexmldata type for associating an XML schema collection with the type. Before anxmldata type column is added to a schema, the schema must first be created in the database by usingCREATE XML SCHEMA COLLECTION. ...
Make it efficient to query the table by date. Leave me with roughly the same table size (mainly adding the size of the index that supports the unique constraint)Are there any drawbacks with this solution except for the fact that you would react on not seeing a primary ...
UNIQUE constraints Constraints are rules that the SQL Server Database Engine enforces for you. For example, you can useUNIQUEconstraints to make sure that no duplicate values are entered in specific columns that don't participate in a primary key. Although both aUNIQUEconstraint and aPRIMARY KEY...