開發課 做練習 學生指南051 les01 ppt
oracle經常兩表連接，叫第三範式，如帶有ID性質的東西
以下是sql語句的命令
select * from departments; 部門表
select * from employees; 員工表
select employee_id,rowid,rownum from employees
where employee_id>=200; 64進制內部運算 rownum本質查詢第幾行
select employee_id,rowid,rownum from employees
where rownum<=5; 查看前5行
select * from employees e where e.department_id=80; 這部門裏的人都有提成
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,處理空行的顯示
select * from employees where manager_id is null; 關於空的處理
select last_name,12*salary*(1+nvl(commission_pct,0)) as anaualsal from employees;進行列別名處理
select last_name,12*salary*(1+nvl(commission_pct,0)) "Anaualsal" from employees;如果要區分大小寫要加雙引號
select last_name ||'xxxx'|| job_id from employees; 連起來顯示
select department_name || q'[ department's manager id:]' || manager_id as "Department and Manager" from departments; q'#xxx# 也可以， 後面就是你想要的東西
select DISTINCT department_id from employees; 有除重必須排序(空有顯示，178號員工沒部門）
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'; 查看用戶範圍內的所有表的所有列
方法2：sqlplus命令
sqlplus /nolog
conn hr/oracle_4U
describe locations 查看錶結構
小提示：選中SQL 按F5看執行計劃
les02 ppt
oracle變量有6種+1形參，兩種宿主
select * from employees where rownum=1;
alter session set nls_date_format='YYYY-MM-DD';修改當前會話默認格式
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);查看多少人是老闆管過人
select * from employees e where e.employee_id not in (select manager_id from employees);這個例子是錯誤的。不能not in 因爲裏頭有空值取反還是空
select * from employees e where e.employee_id not in (select manager_id from employees where manager_id is not null);這樣纔有顯示89個人
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打頭的東西
select * from t05102_a where a like 'A_';查看A打頭的東西
select * from t05102_a where a like '\%%' escape '\'; 查看%號
select * from t05102_a where a like '\_%' escape '\';查看下劃線打頭的
insert into t05102_a values('''');插入單引號
insert into t05102_a values(chr(39)||1); man ascii查看得來的
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;別名,在order by世界裏無所謂是“X”還是a都可以，但是正常語句的sql語句的別名不行
替換變量
select employee_id,salary from employees where employee_id=100;
select employee_id,salary from employees where employee_id=&S_1; 可以進出彈窗，自己選擇ID號
select last_name,salary from employees where last_name like '&S_1%';可以進出彈窗
sqlplus /nolog
select salary from employees where employee_id=&&s_2;問兩次後永遠都是這個
define 默認在這了
undefine s_2 取消
select &&s2,salary from employees where employee_id=&s_2;
set verify off 配置這個後就不會有舊的新的，環境變量