1.select count(*) from employees where last_name like _A%;key:02.select count(*)from employeeswhere to_char(hire_date,YYYY)=1998;select count(*)from employeeswhere hire_date like %98;key:23select to_char(hire_date,YYYY) from employees;3.se
1. select count(*) from employees where last_name like '_A%'; key:0 2. select count(*) from employees where to_char(hire_date,'YYYY')=1998; select count(*) from employees where hire_date like '%98'; key:23 select to_char(hire_date,'YYYY') from employees; 3. select job_title, max_salary-min_salary as "SAL_DIEF" from jobs order by max_salary-min_salary desc; select job_title,(max_salary-min_salary) as "SAL_DIEF" from jobs order by 2 desc; 19行记录 4. select count(*) from employees where (salary>12000 or salary12000; --当它判断1000为假时就不判断后面的大于12000了. select job_id from employees; select * from employees where job_id in('ST_MAN','SH_CLERK'); --工作岗位名称要加单引号 5. select count(*) from employees where to_char(hire_date,'YYYY')=1999 and to_char(hire_date,'mm')=02; key:3 select count(*) from employees where to_char(hire_date,'YYYY-MM')='1999-02'; 6. select last_name,salary, decode(trunc(salary/1500),0,'A', 1,'B', 2,'C', 'D' ) Grade from employees where last_name like'%s'; 7. select d.department_id,d.department_name,l.city from departments d,locations l where d.department_id in(10,40,90) and d.location_id=l.location_id; 8. select l.city,c.country_name,r.region_name from locations l,regions r,countries c where l.location_id=1000 and l.country_id=c.country_id and c.region_id=r.region_id; 9. select m.last_name "MAN_NAME",nvl(e.last_name,'NO EMPLOYEES') "EMP_NAME" from employees m,employees e where m.department_id=100 and m.employee_id=e.manager_id(+); 10行记录 select m.last_name MAN_NAME,nvl(e.last_name,'NO EMPLOYEES') EMP_NAME from employees m,employees e where m.department_id=100 and m.employee_id=e.manager_id(+); 10 select department_id,count(*) NUM from employees where salary>8000 group by department_id ; 9行记录 11 select department_id,count(*) NUM from employees where salary>5000 group by department_id having count(*)>3; 3行记录 12 select last_name,salary from employees where salary> (select salary from employees where employee_id=110) and department_id=100; 2行记录 13 select count(*) NUM from employees where commission_pct<all distinct commission_pct from employees where salary>12000 and commission_pct is not null ); 24行记录 </all>

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。

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。

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。

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“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。

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。


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

AI Hentai Generator
Generate AI Hentai for free.

Hot Article

Hot Tools

ZendStudio 13.5.1 Mac
Powerful PHP integrated development environment

Safe Exam Browser
Safe Exam Browser is a secure browser environment for taking online exams securely. This software turns any computer into a secure workstation. It controls access to any utility and prevents students from using unauthorized resources.

DVWA
Damn Vulnerable Web App (DVWA) is a PHP/MySQL web application that is very vulnerable. Its main goals are to be an aid for security professionals to test their skills and tools in a legal environment, to help web developers better understand the process of securing web applications, and to help teachers/students teach/learn in a classroom environment Web application security. The goal of DVWA is to practice some of the most common web vulnerabilities through a simple and straightforward interface, with varying degrees of difficulty. Please note that this software

SublimeText3 English version
Recommended: Win version, supports code prompts!

VSCode Windows 64-bit Download
A free and powerful IDE editor launched by Microsoft
