97在线影院,欧美一区二区三区的,中文字幕一区二区三区欧美日韩

kangdy

我就像AK47里打出去的子彈。目標TMD永遠在前方。我只能TMD拼命向前。

2011年11月23日

(轉(zhuǎn)貼)數(shù)據(jù)庫連接(內(nèi)連接，外連接，交叉連接)

數(shù)據(jù)庫連接分為：內(nèi)連接，外連接(左、右連接，全連接)，交叉連接
文章地址： http://www.zxbc.cn/html/20080527/51189.html

轉(zhuǎn)載

內(nèi)連接：把兩個表中數(shù)據(jù)對應的數(shù)據(jù)查出來

外連接：以某個表為基礎把對應數(shù)據(jù)查出來（全連接是以多個表為基礎）

student表

no name

1 a

2 b

3 c

4 d

grade表

no grade

1 90

2 98

3 95

內(nèi)連接 inner join（查找條件中對應的數(shù)據(jù)，no4沒有數(shù)據(jù)不列出來）

語法：select * from student inner join grade on student.no = grade.no

結(jié)果

student.no name grade.no grade

1 a 1 90

2 b 2 98

3 c 3 95

左連接（左表中所有數(shù)據(jù)，右表中對應數(shù)據(jù)）

語法：select * from student left join grade on student.no = grade.no

結(jié)果：

student.no name grade.no grade

1 a 1 90

2 b 2 98

3 c 3 95

4 d

右連接（右表中所有數(shù)據(jù)，左表中對應數(shù)據(jù)）

語法：select * from student right join grade on student.no = grade.no

結(jié)果：

student.no name grade.no grade

1 a 1 90

2 b 2 98

3 c 3 95

全連接

語法：select * from student full join grade on student.no = grade.no

結(jié)果：

no name grade

1 a 90

2 b 98

3 c 95

4 d

1 a 90

2 b 98

3 c 95

注：access 中不能直接使用full join ，需要使用union all 將左連接和右連接合并后才可以

交叉連接
將兩個表所有行組合，連接后的行數(shù)為兩個表行數(shù)的乘積（笛卡爾積）
語法，借用上面的例子應該是

select * from student cross join grade

行數(shù)應該為12行：

no name grade

1 a 90

2 b 98

3 c 95

4 d

1 a 90

2 b 98

3 c 95

4 d

1 a 90

2 b 98

3 c 95

4 d

posted @ 2011-11-30 17:24 AK47 閱讀(495) | 評論 (0) | 編輯收藏

JAXB向Xml非根節(jié)點添加一個或多個屬性

JAXB 向Xml非根節(jié)點添加一個或多個屬性，直接上代碼，關(guān)于JAXB的相關(guān)注解可查閱JAVA API。

原創(chuàng)文章，轉(zhuǎn)載請注明出處。http://www.aygfsteel.com/kangdy/archive/2011/11/23/364635.html

code1: colors類根節(jié)點

code1

package com.kangdy.test;

import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement(name = "Colors")
@XmlAccessorType(XmlAccessType.FIELD)
public class Colors {

   @XmlElement(name = "red",nillable=true)
   private Red red;

   @XmlElement(name = "blue",nillable=true)
   private Blue blue;

   public Red getRed() {
       return red;
   }

   public Blue getBlue() {
       return blue;
   }

   public void setRed(Red red) {
       this.red = red;
   }

   public void setBlue(Blue blue) {
       this.blue = blue;
   }
}

code2: Red類子節(jié)點

code2package com.kangdy.test;

import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement(name = "red")
@XmlAccessorType(XmlAccessType.FIELD)
public class Red {

   private String value;

   @XmlAttribute(name = "att1")
   private String att;

   public String getValue() {
       return value;
   }

   public void setValue(String value) {
       this.value = value;
   }

   public String getAtt() {
       return att;
   }

   public void setAtt(String att) {
       this.att = att;
   }

}

code3: 類 Blue 子節(jié)點

code3

package com.kangdy.test;

import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement(name = "blue")
@XmlAccessorType(XmlAccessType.FIELD)
public class Blue {
   private String value;

   @XmlAttribute(name = "att2")
   private String att2;

   @XmlAttribute(name = "att1")
   private String att;

   public String getAtt() {
       return att;
   }

   public void setAtt(String att) {
       this.att = att;
   }

   public String getValue() {
       return value;
   }

   public void setValue(String value) {
       this.value = value;
   }

   public String getAtt2() {
       return att2;
   }

   public void setAtt2(String att2) {
       this.att2 = att2;
   }
}

code4: main類

code4

package com.kangdy.test;

import java.io.StringWriter;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.Marshaller;

public class Jaxbtest {
   public static void main(String[] args) throws Exception {

       StringWriter writer = new StringWriter();
       JAXBContext jc = JAXBContext.newInstance(Colors.class);
       Marshaller ma = jc.createMarshaller();
       ma.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);

       Colors colors = new Colors();
       Red red = new Red();
       red.setAtt("att-red");
       red.setValue("red");
       Blue blue = new Blue();
       blue.setValue("blue");
       blue.setAtt("att-blue");
       blue.setAtt2("blue-att2");
       colors.setRed(red);
       colors.setBlue(blue);

       ma.marshal(colors, writer);
       System.out.println(writer.toString());

   }
}

運行結(jié)果：

結(jié)果

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<Colors>
    <red att1="att-red">
        <value>red</value>
    </red>
    <blue att1="att-blue" att2="blue-att2">
        <value>blue</value>
    </blue>
</Colors>

posted @ 2011-11-23 14:33 AK47 閱讀(10142) | 評論 (4) | 編輯收藏