集合操作

select employee_id, job_id from employees

union all 不去除 保留重復值

select employee_id, job_id from job_history;

select employee_id, job_id from employees

Union 去除重復值

select employee_id, job_id from job_history;

select employee_id, job_id from employees

Intersect 相交

select employee_id, job_id from job_history;

select employee_id from employees

Minus 減

select employee_id from job_history;

select employee_id, job_id, salary from employees

union all

select employee_id, job_id, null from job_history;

select employee_id, job_id, to_char(salary) from employees

union all

select employee_id, job_id, ‘no salary‘ from job_history;

上下相對應

集合排序：

select employee_id, job_id, salary from employees

union all

select employee_id, job_id, null from job_history

order by salary;

select employee_id, job_id, null from job_history

union all

select employee_id, job_id, salary from employees

order by 3;

DML

Create table t1 as select *from employees

Drop table tl;

insert: 插入 字符串

SQL> create table t1(x int, y char(1), z date);

SQL> insert into t1(x, y, z) values (1, ‘a‘, sysdate);

表 數值

SQL> insert into t1(x, z, y) values (2, sysdate+1, ‘b‘);

SQL> insert into t1(x, y, z) values (1, null, sysdate);

SQL> insert into t1(x, z) values (2, sysdate+1);

SQL> insert into t1 values (1, null, sysdate);

所有值都得寫上

SQL> create table my_emp as select * from employees;

SQL> create table my_emp as select last_name, salary from employees where department_id=50;

SQL> create table avg_sal as select department_id, avg(salary) avg_sal from employees group by department_id;

SQL> create table my_emp as select * from employees where 1=0;

SQL> insert into my_emp select * from employees;

update:更新 列

SQL> update my_emp set salary=salary*1.1;

SQL> update my_emp set salary=salary*1.1 where department_id=50;

SQL> update my_emp set salary=salary*1.1, commission_pct=0.5 where employee_id=197;

delete:

SQL> delete from my_emp where employee_id=197;

SQL> delete from my_emp where department_id=50;

SQL> delete from my_emp;

子查詢：

SQL> create table my_emp as select * from employees;

SQL> alter table my_emp add(department_name varchar2(30));

SQL> update my_emp outer set department_name=(select department_name from departments where department_id=outer.department_id);

update (select t1.department_name as aname,t2.department_name bname from my_emp t1 ,departments t2 where t1.department_id=t2.department_id) set aname=bname;

在new_dept表中刪除沒有員工的部門

SQL> create table my_dept as select * from departments;

delete from my_dept outer

where not exists

(select 1 from my_emp

where department_id=outer.department_id);

Commit 結束

delete和truncate：

delete truncate

語句類型 dml ddl

undo數據 產生大量undo數據 不產生undo數據

空間管理 不釋放 釋放

語法 where 刪除全部數據

DDL

字符串：

SQL> create table t1(x char(10), y varchar2(10));

SQL> insert into t1 values(‘x‘, ‘y‘);

SQL> select dump(x), dump(y) from t1;

數值：

SQL> create table t1(x number(5,2), y number(5));

SQL> insert into t1 values (123.45, 12345);

SQL> insert into t1 values (12.345, 12345);

SQL> insert into t1 values (12.345, 123.45);

SQL> select * from t1;

SQL> insert into t1 values (12.345, 112345);

日期時間：

SQL> create table t1(a date, b timestamp, c timestamp with time zone, d timestamp with local time zone);

SQL> insert into t1 values (sysdate, systimestamp, systimestamp, systimestamp);

SQL> alter session set time_zone=‘+9:00‘;

SQL> select * from t1;

修改表結構：

SQL> alter table t1 add(e char(10));

SQL> alter table t1 drop(e);

SQL> alter table t1 modify(d not null);

約束條件：

字段（列）：not null, check(salary>0)

行與行：primary key, unique

表與表之間：foreign key

create table dept (

deptno int constraint dept_deptno_pk primary key,

dname varchar2(20) constraint dept_dname_nn not null);

create table emp (

empno int constraint emp_empno_pk primary key,

ename varchar2(20) constraint emp_ename_nn not null,

email varchar2(50) constraint emp_email_uq unique,

salary int constraint emp_salary_ck check(salary>0),

deptno int constraint emp_deptno_fk references dept(deptno))

SQL> select constraint_name, constraint_type from user_constraints where table_name in(‘DEPT‘, ‘EMP‘);

SQL> insert into emp values (100, ‘abc‘, [email protected], 10000, 10);

insert into emp values (100, ‘abc‘, [email protected], 10000, 10)

*

ERROR at line 1:

ORA-02291: integrity constraint (HR.EMP_DEPTNO_FK) violated - parent key not

found

SQL> insert into dept values (10, ‘sales‘);

1 row created.

SQL> insert into dept values (10, ‘market‘);

insert into dept values (10, ‘market‘)

*

ERROR at line 1:

ORA-00001: unique constraint (HR.DEPT_DEPTNO_PK) violated

SQL> insert into dept values (20, ‘market‘);

1 row created.

SQL> commit;

Commit complete.

SQL> insert into emp values (101, ‘def‘, [email protected], 10000, 20);

create table emp (

empno int constraint emp_empno_pk primary key,

ename varchar2(20) constraint emp_ename_nn not null,

email varchar2(50) constraint emp_email_uq unique,

salary int constraint emp_salary_ck check(salary>0),

deptno int constraint emp_deptno_fk references dept(deptno) on delete set null)或者on delete cascade

Create table tl(x int constraint tl_x_pk primary key);

Alter table tl (add y int);

Alter table tl add(z int ,a int);

Alter table tl frop (z ,a);

Alter table tl modify(y char(1));

Alter table tl modify(y default ‘a’)

Alter table tl disable novalidate constraint tl_x_pk;

Insert into tl values(1,’a’);

Insert into tl values(1,’b’);

Alter table tl enable validate constraint tl_x_pk;

Delete tl;

Alter table tl enable validate constraint tl_x_pk;

Drop table tl;

instead of trigger視圖觸發器 替代觸發器

序列：

SQL> create sequence test_seq increment by 1 start with 1 maxvalue 1000 nocycle cache 20;

SQL> create table t1(x int primary key, y int);

SQL> insert into t1 values (test_seq.nextval, 11); 反復執行

SQL> select * from t1;

Select test_seq.currva from dual 每用一次 序列增長一次

索引：

主鍵和唯一性約束自動創建索引：

SQL> select constraint_name, constraint_type from user_constraints where table_name=‘EMPLOYEES‘;

SQL> select index_name, index_type uniqueness; from user_indexes where table_name=‘EMPLOYEES‘;

SQL> set autot on

SQL> select last_name from employees where employee_id=100; 走索引

SQL> select email from employees; 走索引

SQL> select last_name from employees where salary=2100; 全表掃描

SQL> create index emp_salary_ix on employees(salary);

SQL> select last_name from employees where salary=2100; 走索引

SQL> set autot off

oracle課堂隨筆--第十四天