);-- create indexCREATEINDEXcollege_indexONColleges(college_code); Here, the SQL command creates an index namedcollege_indexon theCollegestable using thecollege_codecolumn. SQL CREATE INDEX Syntax The syntax of
使用CREATE INDEX命令对数据库表创建索引。 提示:SQL 查询准则和建立索引准则可用于帮助您确定要建立索引的列以及要为列创建的索引类型。 语法 CREATE INDEXindex_nameONdatabase_name.table_name[USING { HASH | TREE }] (column_name); index_name值在 ObjectServer 中必须唯一,并且符合 ObjectServer 命名约定。
In SQL Server CREATE INDEX command creates a relational index on a table or view. Also called a rowstore index because it is either a clustered or nonclustered btree index. You can create a rowstore index before there is data in the table. Use a rowstore index to improve query performance,...
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...
The CREATE INDEX command is used to create indexes in tables (allows duplicate values).Indexes are used to retrieve data from the database very fast. The users cannot see the indexes, they are just used to speed up searches/queries.
CREATE [ UNIQUE ] [ CLUSTERED | NONCLUSTERED ] INDEX index_name ON <object> (column [ ASC | DESC ] [ ,...n ] ) [ INCLUDE (column_name [ ,...n ] ) ] [ WHERE <filter_predicate> ] [ WITH ( <relational_index_option> [ ,...n ] ) ] ...
实际上create index CONCURRENTLY需要2次扫描,三次等待。 使用create index(不使用concurrently选项)对表建立索引时,需要对表加Share锁,即5号锁。 Share锁会阻止其它事务对表进行修改(插入、更新和删除)。 使用concurrently选项创建索引时只需要对表加4号锁,允许其它事务对表进行并发修改。
SQL As Understood By SQLite[Contents] CREATE INDEXsql-statement::=CREATE [UNIQUE] INDEX [database-name .] index-name ON table-name ( column-name [, co
Learn more about the Microsoft.SqlServer.TransactSql.ScriptDom.CreateIndexStatement.CreateIndexStatement in the Microsoft.SqlServer.TransactSql.ScriptDom namespace.
DELETE - SQL Command DELETE TAG Command DROP TABLE Command INDEX Command INSERT - SQL Command SELECT - SQL Command SET ANSI Command SET BLOCKSIZE Command SET COLLATE Command SET DELETED Command SET EXACT Command SET EXCLUSIVE Command SET NULL Command SET PATH Command SET REPROCESS Command SET UNIQ...