First, the data definition language:
1, used to change the database structure, including the creation, change and delete database objects;
2, the command:
create table: creation
alter table modify
drop table drop table
Remove truncate table data table (not rollback)
2, create the table:
-- 创建表
create table sclass(
cid int primary key,
cname varchar(10)
)
ssid int primary key, - primary key constraint
sname varchar2 (20) unique, - the only constraint
ssex char (5) check (ssex in ( ' M', 'F')), - check constraints, checks whether the input Male or female
sbirth date not null, - non-empty constraint
saddress varchar2 (50) default 'Zibo', - the default constraint
--score double check (score between 0 and 100), - the wording range check constraint
CID int,
constraint fk_student_class Foreign Key (CID) References sclass is (CID) - foreign key
)
3, modified table structure:
alter table add / modify / drop (add / modify / delete) Column Name Type name / constraints
4, truncation:
truncate table 表名；
- all the records in the table to delete all but retain the table structure, and do not write the log;
- truncate is DDL language,
delete from table name is DML language;
5, delete the table: drop
6, data integrity:
= + Accuracy reliability data integrity
Depending on the scope of the database objects and data integrity mechanism of action, data integrity can be divided into the following four types:
①, entity integrity: the only constraint, primary key constraint;
②, domain integrity: data type restrictions, check constraint, default values, not null constraint;
③, referential integrity (referential integrity): foreign key constraints;
④, self-defined integrity: rules, stored procedures
Data integrity constraints:
Create a table: to ensure the integrity of data integrity constraints embodiments =
Second, the data manipulation language:
Data Manipulation Language:
Retrieve, insert, and modify data (by insert, delete delete, change update, search select)
insert into java values (1, 'John Doe', 'M', to_date ( '1997-02-22', 'yyyy-mm-dd'), 'Jinan');
Date Type Use
to_date
- copy the table (it does not exist) - just copy the table structure, the table data is not copied (since 1 = 2 is not satisfied)
Create Table Student from Java AS SELECT * WHERE 1 = 2;
SELECT * from Student;
- Copy table structure and table of contents, is not bound copy
create table student2 as select * from java;
select * from student2;
- Data from the insertion (can be added before select from) other tables
insert into student select * from java;
select * from student;
Third, transaction control language:
1, the transaction is the smallest unit of work, work as a whole
2, to ensure the overall success or failure of the transaction, known as transaction control;
3, for transaction control statements are:
commit: commit and terminate the transaction;
rollback: Undo transaction completed work;
savepoint: marked transaction can be rolled back to the point;
Fourth, data control language:
1, the control data provides access control language for the user language;
2, the command:
grant: grant permission;
revoke: revoke permissions have been granted;
- Create a user
the Create the User YYM IDENTIFIED by 123456;
Grant Connect, Resource to YYM; - grant permission
- Log administrator account, the user can set permissions to access yym scott.emp table (view only)
Grant the SELECT ON scott.emp to yym with the Option Grant;
select * from scott.emp;
- Undo yym administrator access rights that table just
revoke select on scott.emp from yym;