The EXPLAIN command will fail if you use it for other SQL commands, such as data definition language (DDL) or database operations. The EXPLAIN output relative unit costs are used by Amazon Redshift to choose a
The DB2 installation should come with a script that can be used to create the explain plan tables. The script is called EXPLAIN.DDL and should be located in the MISC directory under the DB2 installation directory. Oracle:For Oracle, to perform an explain plan, the PLAN_TABLE must exist. Fo...
Calling theSYSPROC.SYSINSTALLOBJECTSprocedure is preferred over using theEXPLAIN.DDLfile since it can automatically adapt to different database configurations. For example, ifBLOCKNONLOGGEDparameter is set to yes, then some statements inEXPLAIN.DDLfail becauseNOT LOGGEDclause is used for LOB columns. H...
If the FE node version and SE version are inconsistent with the schema version, schema latency may occur. If a large number of DDL statements are executed on the partitioned parent table, the processing speed of SE is slow and the latency is high. As a result, data write and read are ...
up to deal with.For example: Ok, got it OceanBase Data V4.2.1 What is OceanBase Database Get Started Develop Deploy Migrate Manage OBKV Reference System principles System management Database object management Database design
Note:The EXPLAIN command cannot be used for the Database operations and DDL commands other than creating a table, insert, delete, select, select into and update. Examples of Redshift EXPLAIN Given below are the examples to see the implementation of the EXPLAIN command with SQL queries: ...
# db/migrate/***_remove_null_index.rbclassRemoveNullIndex<ActiveRecord::Migration::Currentdisable_ddl_transaction!defchangeremove_index:users,name: :index_users_on_discarded_at,algorithm: :concurrently,column: :discarded_atadd_index:users,:discarded_at,where:"discarded_at IS NOT NULL",algorithm: ...
SQL语句主要分为 DDL语句:数据定义语⾔,这些语句定义了不同的数据段、数据库、表、列、索引等数据库对象。 DML语句:数据操纵语句,⽤于添加、删除、更新、和查询数据库记录,并检...为什么要学集合源码? 1.学习集合源码,能够让我们使用得更加准确。 当我们深入学习了源码之后,我们就能够了解其特性,从而能够根据...
TheEXPLAINPLANstatement is a data manipulation language (DML) statement, rather than a data definition language (DDL) statement. Therefore, Oracle Database does not implicitly commit the changes made by anEXPLAINPLANstatement. If you want to keep the rows generated by anEXPLAINPLANstatement in the...
用于配置是否允许DDL操作的权限,默认值为1。 可设置的值如下:0: 不允许DDL查询。1: 允许DDL查询。 如果当前会话的allow_ddl=0,则无法执行: SET allow_ddl=0。 26.4.5.用户管理配置 xml文件的users标签的结构如下: <users> <!-- If user name was not specified, 'default' user is used. --> <user...