Oracle在表中删除数据的语法是: 语法结构: DELETE FROM表名 WHERE 条件 代码演示: SQL DELETE FROM INFOS WHERE STUID=s100103; 1 ROW DELETED SQL COMMIT; TRUNCATE 在数据库操作中, TRUNCATE命令(是一个DDL命令)可以把表中的所有数据一次性全部删除
Oracle在表中删除数据的语法是:
语法结构:
DELETE FROM表名 WHERE 条件
代码演示:
SQL> DELETE FROM INFOS WHERE STUID='s100103'; 1 ROW DELETED SQL> COMMIT;
TRUNCATE
在数据库操作中, TRUNCATE命令(是一个DDL命令)可以把表中的所有数据一次性全部删除,语法是:
语法结构:
TRUNCATE TABLE 表名
TRUNCATE和DELETE都能把表中的数据全部删除,他们的区别是:
1、TRUNCATE是DDL命令,删除的数据不能恢复;DELETE命令是DML命令,删除后的数据可以通过日志文件恢复。
2、如果一个表中数据记录很多,TRUNCATE相对DELETE速度快。
由于TRUNCATE命令比较危险,因此在实际开发中,TRUNCATE命令慎用。

oracle asm指的是“自动存储管理”,是一种卷管理器,可自动管理磁盘组并提供有效的数据冗余功能;它是做为单独的Oracle实例实施和部署。asm的优势:1、配置简单、可最大化推动数据库合并的存储资源利用;2、支持BIGFILE文件等。

方法:1、利用“select*from user_indexes where table_name=表名”语句查询表中索引;2、利用“select*from all_indexes where table_name=表名”语句查询所有索引。

在oracle中,可以利用“TO_SINGLE_BYTE(String)”将全角转换为半角;“TO_SINGLE_BYTE”函数可以将参数中所有多字节字符都替换为等价的单字节字符,只有当数据库字符集同时包含多字节和单字节字符的时候有效。

在Oracle中,可利用lsnrctl命令查询端口号,该命令是Oracle的监听命令;在启动、关闭或重启oracle监听器之前可使用该命令检查oracle监听器的状态,语法为“lsnrctl status”,结果PORT后的内容就是端口号。

在oracle中,可以利用“drop sequence sequence名”来删除sequence;sequence是自动增加数字序列的意思,也就是序列号,序列号自动增加不能重置,因此需要利用drop sequence语句来删除序列。

方法:1、利用“LOWER(字段值)”将字段转为小写,或者利用“UPPER(字段值)”将字段转为大写;2、利用“REGEXP_LIKE(字符串,正则表达式,'i')”,当参数设置为“i”时,说明进行匹配不区分大小写。

在oracle中,可以利用“select ... From all_tab_columns where table_name=upper('表名') AND owner=upper('数据库登录用户名');”语句查询数据库表的数据类型。

方法:1、利用“alter system set sessions=修改后的数值 scope=spfile”语句修改session参数;2、修改参数之后利用“shutdown immediate – startup”语句重启服务器即可生效。


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