由于数据压缩比更好,一方面节省了磁盘空间,另一方面对于cache也有了更大的发挥空间 DBMS的功能:几乎覆盖了标准SQL的大部分语法,包括DDL和DML,以及配套的各种函数,用户管理及权限管理,数据的备份与恢复; 多样化引擎:ClickHouse和MySQL类似,把表级的存储引擎插件化,根据表的不同需求可以设定不同的存储引擎。目前包括合并树...
检查SQL语句中的表是否已创建列索引:存储过程dbms_imci.check_columnar_index()能够解析输入的SQL语句,提取该语句中使用的所有列,并验证这些列是否被列索引所覆盖。 获取创建列存索引的DDL语句:存储过程dbms_imci.columnar_advise()可以针对输入的SQL语句,生成相应的用于添加列存索引的DDL语句。执行后,可以确保该SQL语...
人工采集 快照默认是自动采集的,但您也可以按需要采集它们。所有的 AWR 功能都在程序包DBMS_WORKLOAD_REPOSITORY 中实施。要采集一次快照,只需发出下面的命令: execute dbms_workload_repository.create_snapshot 它立即采集一次快照,快照被记录在表 WRM$_SNAPSHOT 中。采集的量度是针对 TYPICAL 级别的。 如果您想采...
2.创建测试表演示获取执行计划 scott@ORCL> create table t as select * from all_objects where rownum<=1000; Table created. --加载创建表的执行计划(DDL 执行计划) scott@ORCL> explain plan set statement_id='T1' for create table t1 as select * from t; Explained. --使用下面的语句从plan_table...
scott@ORCL>create table tasselect*from all_objects where rownum<=1000;Table created.--加载创建表的执行计划(DDL执行计划)scott@ORCL>explain plansetstatement_id='T1'forcreate table t1asselect*from t;Explained.--使用下面的语句从plan_table 获取执行计划 ...
Typically, the DB2 installation comes with a script namedEXPLAIN.DDLthat contains the CREATE TABLE and CREATE INDEX statements for these tables. The script is often inMISCdirectory under your DB2 server installation folder. DB2 version 8.x execution plan tables are listed below: ...
scott@ORCL> create table t as select * from all_objects where rownum<=1000; Table created. --加载创建表的执行计划(DDL 执行计划) scott@ORCL> explain plan set statement_id='T1' for create table t1 as select * from t; Explained. --使用下面的语句从plan_table 获取执行计划 col OPERATION fo...
--加载创建表的执行计划(DDL 执行计划) scott@ORCL> explain plan set statement_id='T1' for create table t1 as select * from t; Explained. --使用下面的语句从plan_table 获取执行计划 col OPERATION format a25 col OPTIONS format a25 col OBJECT_NAME format a25 ...
DDL commands other than the ones specified in the article. In case, if you want to retrieve the summarized information of the execution plan then you can skip the specification of the optional parameter VERBOSE while to get the detailed information of execution flow you can specify VERBOSE in ...
What function does an attribute of an entity perform in a DBMS? Write a database description for each of the relations shown using SQL DDL. Assume the following attribute data types: StudentID (integer, primary key) StudentName (25 characters) Facult...