CREATE UNIQUE INDEX index1 ON schema1.table1 (column1 DESC, column2 ASC, column3 DESC); 主要方案: 从Azure SQL 数据库和 Azure SQL 托管实例中的 SQL Server 2016(13.x)开始,可以在列存储索引上使用非聚集索引来提高数据仓库查询性能。 有关详细信息,请参阅 列存储索引 - 数据仓库。 有关其他类型...
So, to speed up data retrieval, SQL Server has a special data structure called indexes. An index is mostly created on one or more columns which are commonly used in the SELECT clause or WHERE clause. There are two types of indexes in SQL Server:...
Should there be only one column used, a single-column index should be the choice. Should there be two or more columns that are frequently used in the WHERE clause as filters, the composite index would be the best choice 不适合使用索引的场景 Indexes should not be used on small tables Table...
ON [database_name. [ schema_name ] . | schema_name . ]table_name 指定包含该索引的由一部分、两部分或三部分名称组成的表。 非聚集列存储的 ORDER 非聚集列存储索引子句中指定的ORDER列必须是索引的键列的子集。 column_store_order_ordinal使用sys.index_columns中的列来确定非聚集列存储索引的列的顺序...
CREATE TABLE (Transact-SQL) 從SQL Server 2016 (13.x) 開始,您可以建立具有資料行存放區索引的記憶體最佳化資料表。 建立資料表之後,也可以使用 ALTER TABLE ADD INDEX 語法來加入資料行存放區索引。 將資料載入資料行存放區索引。 列存儲索引資料載入 刪除列存放區索引。 DROP INDEX (Transact-SQL) 使用B ...
sql server 视图新增唯一字段 sql server视图创建语法 1、说明:增加、删除一个列 Alter table tablename add columnName col type alter table tablename drop columnName column_b 2.添加删除主键 alter table tableName add constraint PK_Name primary key(Name)...
In table-valued user-defined functions, the PRIMARY KEY constraint can be created on only one column per table. PRIMARY KEY can't be specified for CLR table-valued functions. UNIQUE A constraint that provides entity integrity for a specified column or columns through a unique index. A table ...
User must be a member of the sysadmin fixed server role or the db_ddladmin and db_owner fixed database roles. Using SQL Server Management Studio to create an index with nonkey columns In Object Explorer, select the plus sign to expand the database that contains the table on which you ...
A SQL Server Computed Column is a virtual column that is not stored physically on the table, unless it is previously specified as PERSISTED.
Creates a unique index on a table or view. A unique index is one in which no two rows are permitted to have the same index key value. A clustered index on a view must be unique. The SQL Server 2005 Database Engine does not allow creating a unique index on columns that already includ...