开发课 做练习 学生指南051 les01 ppt
oracle经常两表连接，叫第三范式，如带有ID性质的东西
以下是sql语句的命令
select * from departments; 部门表
select * from employees; 员工表
select employee_id,rowid,rownum from employees
where employee_id>=200; 64进制内部运算 rownum本质查询第几行
select employee_id,rowid,rownum from employees
where rownum<=5; 查看前5行
select * from employees e where e.department_id=80; 这部门里的人都有提成
select last_name,12*salary*(1+commission_pct) from employees; 查看年收入
select last_name,12*salary*(1+nvl(commission_pct,0)) from employees; 查看年收入,处理空行的显示
select * from employees where manager_id is null; 关于空的处理
select last_name,12*salary*(1+nvl(commission_pct,0)) as anaualsal from employees;进行列别名处理
select last_name,12*salary*(1+nvl(commission_pct,0)) "Anaualsal" from employees;如果要区分大小写要加双引号
select last_name ||‘xxxx‘|| job_id from employees; 连起来显示
select department_name || q‘[ department‘s manager id:]‘ || manager_id as "Department and Manager" from departments; q‘#xxx# 也可以， 后面就是你想要的东西
select DISTINCT department_id from employees; 有除重必须排序(空有显示，178号员工没部门）
create table t05101_distinct (a varchar2(10),b varchar2(10));
insert into t05101_distinct values (‘A‘,‘B‘);
select * from t05101_distinct;
select distinct a,b from t05101_distinct;
insert into t05101_distinct values (‘A‘,‘B1‘); 除重是除掉整行
select distinct a,b from t05101_distinct;
select * from user_tab_cols tc where tc.TABLE_NAME=‘LOCATIONS‘; 查看用户范围内的所有表的所有列
方法2：sqlplus命令
sqlplus /nolog
conn hr/oracle_4U
describe locations 查看表结构
小提示：选中SQL 按F5看执行计划
les02 ppt
oracle变量有6种+1形参，两种宿主
select * from employees where rownum=1;
alter session set nls_date_format=‘YYYY-MM-DD‘;修改当前会话默认格式
select last_name from employees where hire_date = to_date(‘17-JUN-07‘,‘DD-MON-RR‘);
select * from employees e where e.employee_id in (select manager_id from employees);查看多少人是老板管过人
select * from employees e where e.employee_id not in (select manager_id from employees);这个例子是错误的。不能not in 因为里头有空值取反还是空
select * from employees e where e.employee_id not in (select manager_id from employees where manager_id is not null);这样才有显示89个人
create table t05102_a (a varchar2(10));
insert into t05102_a values (‘A‘);
insert into t05102_a values (‘A1‘);
insert into t05102_a values (‘%‘);
insert into t05102_a values (‘_‘);
insert into t05102_a values (‘_1‘);
select * from t05102_a;
select * from t05102_a where a like ‘A%‘; A打头的东西
select * from t05102_a where a like ‘A_‘;查看A打头的东西
select * from t05102_a where a like ‘\%%‘ escape ‘\‘; 查看%号
select * from t05102_a where a like ‘\_%‘ escape ‘\‘;查看下划线打头的
insert into t05102_a values(‘‘‘‘);插入单引号
insert into t05102_a values(chr(39)||1); man ascii查看得来的
create table t05102_b (a number,b number);
insert into t05102_b values(1,999);
insert into t05102_b values(1,0);
insert into t05102_b values(2,999);
insert into t05102_b values(2,0);
select * from t05102_b order by a,b;先按a排列在按照b排列
select * from t05102_b order by a desc ,b desc;
select a "X", b "Y" from t05102_b order by "X" desc,"Y" desc;别名,在order by世界里无所谓是“X”还是a都可以，但是正常语句的sql语句的别名不行
替换变量
select employee_id,salary from employees where employee_id=100;
select employee_id,salary from employees where employee_id=&S_1; 可以进出弹窗，自己选择ID号
select last_name,salary from employees where last_name like ‘&S_1%‘;可以进出弹窗
sqlplus /nolog
select salary from employees where employee_id=&&s_2;问两次后永远都是这个
define 默认在这了
undefine s_2 取消
select &&s2,salary from employees where employee_id=&s_2;
set verify off 配置这个后就不会有旧的新的，环境变量