DROP INDEX 语句 DROP INDEX语句用于删除表中的索引。 MS Access: DROPINDEX index_nameONtable_name; SQL Server: DROPINDEX table_name.index_name; DB2/Oracle: DROPINDEX index_name; MySQL: ALTERTABLEtable_name DROPINDEX index_name; 通过这些 SQL 语句,您可以在数据库中创建索引,提高数据检索的效率。如...
CREATE INDEX 示例 下面的 SQL 语句在 "Persons" 表的 "LastName" 列上创建一个名为 "idx_lastname" 的索引: 如果要在多列的组合上创建索引,可以在括号内列出列名,用逗号分隔: DROP INDEX 语句 语句用于删除表中的索引。 MS Access: SQL Server: DB2/Oracle: MySQL: 通过这些 SQL 语句,您可以在数据库中...
CREATE INDEX 实例 以下的 SQL 语句在 "Persons" 表的 "LastName" 列上创建一个名为 "PIndex" 的索引: CREATEINDEXPIndexONPersons (LastName) 假设您希望索引不止一个列。您能够在括号里列出这些列的名称,用逗号隔开: CREATEINDEXPIndexONPersons (LastName, FirstName) Oracle 语法: CREATE UNIUQE | BITMAP...
Oracle Database supports several types of index: Normal indexes. (By default, Oracle Database creates B-tree indexes.) Bitmap indexes, which store rowids associated with a key value as a bitmap. Partitioned indexes, which consist of partitions containing an entry for each value that appears...
SQL 型 V4.3.0参考指南SQL 参考SQL 语法普通租户(Oracle 模式)SQL 语句 DDL CREATE INDEX CREATE INDEX 更新时间:2024-04-29 11:21:53 编辑 分享 描述该语句用来创建索引。索引是创建在表上的,对数据库表中一列或多列的值进行排序的一种结构。其作用主要在于提高查询的速度,降低数据库系统的性能开销。OceanBas...
INDEX_NAME LOGGING STATUS --- --- --- IDX_T_INDEX YES VALID SQL> drop index idx_t_index; Index dropped. SQL> create index idx_t_index on t_index(a) nologging; Index created. SQL> select index_name,logging,status from user_indexes where...
schema ORACLE模式,缺省即为当前帐户 index 索引名 table 创建索引的基表名 column 基表中的列名,一个索引最多有16列,long列、long raw 列不能建索引列 DESC、ASC 缺省为ASC即升序排序 CLUSTER 指定一个聚簇(Hash cluster不能建索引) INITRANS、MAXTRANS 指定初始和最大事务入口数 ...
CREATE UNIQUE INDEX custcode ON customer(cust_code); Output: Create Index in MySQL, PostgreSQL, Oracle, SQL Server Create Index in MySQL [5.7] Without an index, MySQL must begin with the first row and then read through the entire table to find the relevant rows. The larger the table, th...
PostgreSQL, Oracle DROPINDEXcollege_index; MySQL ALTERTABLECollegesDROPINDEXcollege_index; Here, the SQL command removes an index namedcollege_indexfrom theCollegestable. Note:Deleting an index in SQL means only the index is deleted. The data in the original table remains unaltered. ...
DROP INDEX 敘述句 (SQL DROP INDEX Statement) 我們要怎麼將索引移除掉?就是使用 DROP INDEX。 MySQL ALTERTABLEtable_nameDROPINDEXindex_name; SQL Server DROPINDEXtable_name.index_name; Oracle DROPINDEXindex_name; MS Access DROPINDEXindex_nameONtable_name;...