ClickHouse是俄罗斯的Yandex于2016年开源的列式存储数据库(DBMS),使用C++语言编写,主要用于在线分析处理查询(OLAP),能够使用SQL查询实时生成分析数据报告。 OLAP(On-Line Analytical Processing)翻译为联机分析处理,专注于分析处理,从对数据库操作来看,OLAP是对数据的查询; OLTP(on-line transaction processing)翻译为联机...
When a view cannot be merged into the main query you will often see a projection view operation. This indicates that the 'view' will be selected from directly as opposed to being broken down into joins on the base tables. A number of constructs make a view non mergeable. Inline views ar...
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$_SNAPSHOT 中。采集的量度是针对 TYPICAL 级别的。 如果您想采集更详细的统计数据,您可以在上面的过程中将参数 FLUSH_LEVE...
pk_increment]), range(MIN ; MAX)always true | +---+ 14 rows in set obclient> SELECT DBMS_XPLAN.DISPLAY('TYPICAL',null,'test')\G *** 1. row *** DBMSXPLAN.DISPLAY('TYPICAL',null,'test'): === |ID|OPERATOR |NAME|EST.ROWS|EST.TIME(us)| ---...
select plan_table_output from table(dbms_xplan.display()); 3.通过第3方工具,如plsql developer(f5查看执行计划)、toad等; 1. 2. 3. 4. 5. 6. 7. 三、看懂执行计划 1.执行计划中字段解释 1. SQL> select * from scott.emp a,scott.emp b where a.empno=b.mgr; ...
dbms_xplan,display explain plan,explain plan,how to generate explain plan,ORA-02404: specified plan table not found,plan table does not exist,PLAN_TABLE This post is to demonstrate the ways to create and display explain plan. But before we proceed with the steps of creating and displaying exp...
>>Note the drop-down control added to the Explain Plan button in the worksheet toolbar. This is a total disaster. Please make an option to disable this “feature” or just disable it. This “feature” blocks using dbms_xplan. I typically use gather_plan_statistics hint and select * fro...
How to create a table in MySQL If a 1:M relationship is optional on the 1 side and mandatory on the M side, which of the following is true? The resulting foreign key can have null (empty) values. The resulting foreign key cannot ha What is...
12.1.3.1 Using V$SQL_PLAN Views In addition to running the EXPLAIN PLAN command and displaying the plan, you can use the V$SQL_PLAN views to display the execution plan of a SQL statement: After the statement has executed, you can display the plan by querying the V$SQL_PLAN view. V$SQL...
For the Oracle's cost-based optimizer (CBO) to work correctly, you need to regularly compute statistics for your tables and indexes using the Oracle-suppliedDBMS_STATSpackage or theANALYZE TABLEstatement. DB2 Explain Plan Visual explain plan is supported for DB2 versions 8.x and 9.x. It is...