DDL(数据定义语言,Data Definition Language):DDL代表数据定义语言,是一种有助于创建数据库模式的SQL命令。DDL中常用的命令有:create,drop,alter,truncate和rename等等。 DML(数据操作语言,Data Manipulation Language):DML代表数据操作语言,是一种有助于检索和管理关系数据库中数据的SQL命令。DML中常用的命令有:insert,...
在使用TRUNCATE命令时,需要注意其自动提交事务的特性,并且可以选择是否重置标识列的值。与DELETE语句相比,TRUNCATE具有更高的执行效率和更少的日志记录,但缺少了一些操作灵活性和回滚能力。 参考资料: •[SQL TRUNCATE TABLE]( •[What is the difference between TRUNCATE and DELETE in SQL](...
In SQL, the TRUNCATE TABLE statement is a Data Definition Language (DDL) operation that marks the extents of a table for deallocation (empty for reuse). The result of this operation quickly removes all data from a table, typically bypassing a number of integrity enforcing mechanisms. It was ...
DELETE和TRUNCATE等语句来删除数据。这些语句是SQL语言中的最常用的命令，且它们有着不同的含义和使用场景...
Following is the sequence of events When a truncate/drop occurs: 1. Foreground process acquires the "RO" enqueue in exclusive mode 2. Cross instance calls (or one call if it is a single object) are issued ("CI" enqueue is acquired) ...
(因此,这不是错误,而是预期的行为。仅当对象实际更改时,Last_ddl_time才会更新。) 所以有可能是原表就是空表,你做truncate操作的时候,实际上就不会更新last_ddl_time这个列。 测试模拟 [oracle@oracle ~]$ sqlplus/assysdba SQL*Plus: Release11.2.0.4.0ProductiononTue Apr2808:34:312020Copyright (c)1982,...
4.当执行以上DDL语句时,事务自动提交 三、详细说明 1.增加列: 语法: 代码语言:javascript 复制 alter table tb_name add column datatype[defaultval]constraint... 说明: 1.如果添加not null(primary key约束要求值也不能为null)约束,需要保证当前表中没有数据存在 2....
SQL复制 -- Create table Student with partition>CREATETABLEStudent (nameSTRING, rollnoINT) PARTITIONEDBY(ageINT); >SELECT*FROMStudent; name rollno age--- --- ---ABC 1 10 DEF 2 10 XYZ 3 12-- Remove all rows from the table in the specified partition>TRUNCATETABLEStudentpartition(...
SQL> alter table tb_reuse deallocate unused keep 2048; --这里漏掉了指定m,缺省为byte Table altered. Elapsed: 00:00:00.36 SQL> select segment_name,bytes/1024/1024 from dba_segments where segment_name in('TB_REUSE','TB_NOREUSE');
Access Code - DELETE Statement with DISTINCTROW and T-SQL Access Now() vs. T-SQL GETDATE() ? ADD and SUBTRACT depending on the condition is CASE STATEMENT ADD COLUMN to variable table? Add prefix in data column Add Time in SQL HH:MM:SS to another HH:MM:SS Adding a column to a lar...