);-- 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 the SQLCREATE INDEXstatement is: CREATEINDEXindex_nameONtable_name (column_name1, colu...
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。
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.
SQL 复制 CREATE INDEX index1 ON schema1.table1 (column1); 在表上创建聚集索引,并为表使用由 3 个部分组成的名称 SQL 复制 CREATE CLUSTERED INDEX index1 ON database1.schema1.table1 (column1); 使用唯一约束创建非聚集索引并指定排序顺序 SQL 复制 CREATE UNIQUE INDEX index1 ON schema1.tab...
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。
Note Candidate indexes (created by including the UNIQUE option in CREATE TABLE or ALTER TABLE – SQL) are not the same as indexes created with the UNIQUE option in the INDEX command. An index created with the UNIQUE option in the INDEX command allows duplicate index keys; candidate indexes do...
SQL As Understood By SQLite[Contents] CREATE INDEXsql-statement::=CREATE [UNIQUE] INDEX [database-name .] index-name ON table-name ( column-name [, co
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...
Visual FoxPro uses the default value if you use the SQL ALTER TABLEcommand to remove autoincrementing for the field.PRIMARY KEY | UNIQUE PRIMARY KEY creates a primary index for the field specified in FieldName1. UNIQUE creates a candidate index for the field specified in FieldName1. The ...