2种连接数据库和读取sql文件添加数据库和表
import java.io.*;
import java.sql.*;
public class DBConn {
private String ADDRESS ;
private int PORT ;
private String DBNAME ;
private String USERNAME ;
private String PASSWORD ;
private Connection conn ;
private PreparedStatement pstmt ;
private Statement stmt ;
private ResultSet rs ;
/***
* 连接MYSQL数据库
* @return
*/
public Connection getMySqlConn(){
try{
ADDRESS = "127.0.0.1";
PORT = 3306;
DBNAME = "test";
USERNAME = "root";
PASSWORD = "123456";
if(conn==null){
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection("jdbc:mysql://"+ADDRESS+":"+PORT+"?user="+USERNAME+"&password="+PASSWORD+"&useUnicode=true&characterEncoding=utf8");
}
}catch(Exception e){
e.printStackTrace();
}
return conn;
}
/***
* 连接MSSQL数据库
* @return
*/
public Connection getMSSqlConn(){
try{
ADDRESS = "127.0.0.1";
PORT = 1433;
DBNAME = "mytest";
USERNAME = "sa";
PASSWORD = "";
if(conn==null){
Class.forName("net.sourceforge.jtds.jdbc.Driver");
conn = DriverManager.getConnection("jdbc:jtds:sqlserver://"+ADDRESS+":"+PORT,USERNAME,PASSWORD);
}
}catch(Exception e){
e.printStackTrace();
}
return conn;
}
/**
* 关闭数据库连接
* @return
*/
public void closeConn(){
try{
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A。
SQL语句的并集UNION,交集JOIN(内连接,外连接),交叉连接(CROSS
JOIN笛卡尔积),差集(NOT IN)
1.
a. 并集UNION
SELECT column1, column2 from table1
UNION
SELECT column1, column2 from table2
b. 交集JOIN
SELECT * from table1 AS a JOIN table2 b ON a.name=b.name
c. 差集NOT IN
SELECT * from tabl ......
SQL分页
万能分页
.net代码
select top 每页显示的记录数 * from topic where id not in
(select top (当前的页数-1)×每页显示的记录数 id from topic order by id desc)  ......
string s = " 80,81,83,82";
string[] s1 = s.Split(',');
int[] p = new int[s1.Count()];
for (int i = 0; i < s1.Count( ......
1.按姓氏笔画排序: Select * from TableName Order By CustomerName Collate Chinese_PRC_Stroke_ci_as
2.数据库加密: select encrypt('原始密码') select pwdencrypt('原始密码') select pwdcompare('原始密码','加密后密码') = 1--相同;否则不相同
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上节我们介绍了表连接,更确切的说是inner joins內连接.
內连接仅选出两张表中互相匹配的记录.因此,这会导致有时我们需要的记录没有包含进来。
为更好的理解这个概念,我们介绍两个表作演示。苏格兰议会中的政党表(party)和议员表(msp)。
party(Code,Name,Leader)
Code: 政党代码
Name: 政党 ......