JAVA41: Database Five (Oracle)

Database design:

Three-paradigm (old)

Column values are unique and cannot have duplicate column values

property is completely dependent on the primary key

Must meet the first paradigm

Must have a primary key

The other columns must be fully dependent on the primary key

property is not dependent on other non-primary properties (second enhancement)

Must satisfy the second paradigm

Removal of transitive dependencies

(In a specific case, the efficiency of the consideration, such as: specifically to do redundancy, do not adhere to the third)

Oracle sequence

A sequence can be used to generate a primary key for a single table service, or multiple

Create a sequence

Create sequence sequence name start with numeric Incremet by value

| Do not write is 1 |

Delete a sequence

Drop Sequence sequence Name

Get the next value from a pseudo-column nextval

Select Seq_stu.nextval from dual;

Gets the current value Currval

Select Seq_stu.currval from dual;

Create sequence Seq_stu start with Incremet by5;select seq_stu.nextval from Dual;insert to Stu (ID) VALUES (SEQ_STU.N Extval);

Complete:

CREATE TABLE Stu (s_id number, s_name varchar2 (), Constraint S_PK primary key (s_id)) Create sequence Seq_stu start With + increment by 5;select * from Stu;

Package Jdbc;public class Stu {private int id;private String name;public int getId () {return ID;} public void setId (int id) {this.id = ID;} Public String GetName () {return name;} public void SetName (String name) {this.name = name;}}

package jdbc;import java.sql.connection;import  Java.sql.preparedstatement;public class studao {private static final string  SQL =  "Insert into stu (s_id,s_name)  values (Seq_stu.nextval,?)"; Public void save (Stu stu)  throws exception{connection con = null;try{ Con = dbutils.getconnection (); Preparedstatement stmt = con.preparestatement (SQL); Stmt.setstring (1,stu.getname ()); Stmt.executeupdate ();} catch (exception e) {throw e;} Finally{if (con != null) {con.close ();}}}} 

Package Jdbc;import static Org.junit.assert.*;import Org.junit.test;public class Teststudao {@Testpublic void Test () Throws Exception {Studao s = new Studao (); Stu ss = new Stu (); Ss.setname ("Lmdtx"); S.save (ss);}}

er Diagram (open source community has the truth)

Find what you like or what your company is used to (tools) A4 paper

Research business needs

Designing and drawing E-r diagrams

Design document

Write what you need to write.

This article is from the "Romantic Laugh" blog, make sure to keep this source http://lmdtx.blog.51cto.com/6942028/1840339

JAVA41: Database Five (Oracle)