数字条件：
SQL> select salary from employees where employee_id=100;
字符串大小写敏感：
SQL> select last_name, salary from employees where last_name=‘King‘;
SQL> select table_name, tablespace_name from user_tables where table_name=‘EMPLOYEES‘;
lower()
日期格式敏感：
select sysdate from dual
SQL> alter session set nls_date_format=‘RR-Mon-dd‘;
SQL> select last_name from employees where hire_date=‘2006-05-23‘;
SQL> select last_name from employees where hire_date=to_date(‘2006-05-23‘, ‘yyyy-mm-dd‘);
区间查询：
SQL> select last_name from employees where salary>=3400 and salary<=4000;
SQL> select last_name from employees where salary between 3400 and 4000;
SQL> select last_name from employees where salary between 3000 and 5000 and department_id=50;
in：
SQL> select last_name from employees where department_id=30 or department_id=40 or department_id=50;
SQL> select last_name from employees where department_id in (30, 40, 50);
通配符：
SQL> select last_name, job_id from employees where job_id like ‘%\_MAN‘ escape ‘\‘;
null作为条件：
SQL> select last_name from employees where commission_pct is null;
SQL> select last_name from employees where commission_pct is not null;
and/or/not：
SQL> select last_name, job_id, department_id, salary from employees where job_id=‘SA_REP‘ or department_id=50 and salary>=8000;
SQL> select last_name, job_id, department_id, salary from employees where (job_id=‘SA_REP‘ or department_id=50) and salary>=8000;
排序：
SQL> select last_name, salary from employees order by salary; 列名 默认升序
SQL> select last_name, salary from employees order by salary desc; 降序
SQL> select last_name, salary from employees order by last_name; 字符串左对齐对比ascii码
SQL> select last_name, hire_date from employees order by hire_date; 日期按时间轴排序
SQL> select last_name, salary, commission_pct from employees order by salary desc, commission_pct desc;
SQL> select last_name, salary*12*(1+commission_pct) from employees order by 2;列参数
SQL> select last_name, salary*12*(1+commission_pct) total_salary from employees order by total_salary;起别名