select num,count(num) from T group by num order by count(num) desc; 

package com.softsec.demo;
import java.util.HashMap;
import java.util.Map;
import java.util.Random;
/**
 * 查找數(shù)組中重復(fù)元素和重復(fù)元素的個數(shù)
 * @author chenhh
 *
 */
public class getRepeat {
	/**
	 * 循環(huán)比較處理
	 * @param arr
	 */
	public static void cyclingDemo ( int[] arr){
		for (int x = 0; x < 10; x++) {
			int sumber1 = 0;
			for (int j = 0; j < 20; j++) {
				//數(shù)組中的數(shù)循環(huán)比較
				if (x == arr[j]) {
					sumber1++;
				} else {
					continue;
				}
			}
			System.out.println(x + " -- 重復(fù)個數(shù):" + sumber1);
		}
	}
	public static void main (String[] args){
		Random random = new Random();
		int[] arr = new int[20];
		for (int i = 0; i < 20; i++) {
			arr[i] = random.nextInt(10);
			if (i < arr.length - 1) {
				System.out.print(arr[i]+"，");
			} else {
				System.out.print(arr[i] + "\r\n 結(jié)果：" + "\r\n" );
			}
		}
		// 輸出arr數(shù)組中重復(fù)元素，重復(fù)數(shù)量
		// 循環(huán)處理
		cyclingDemo(arr);
		// map處理
		// mapDemo(arr);
	}

package com.softsec.demo;
import java.util.HashMap;
import java.util.Map;
import java.util.Random;
/**
 * 查找數(shù)組中重復(fù)元素和重復(fù)元素的個數(shù)
 * @author chenhh
 *
 */
public class getRepeat {
	/**
	 * 轉(zhuǎn)成集合處理
	 * @param arr
	 */
	public static void mapDemo ( int[] arr){
		//將數(shù)據(jù)轉(zhuǎn)成集合
		Map<Integer, Integer> map = new HashMap();
		for (int a = 0; a < arr.length; a++) {
			if (map.get(arr[a])!=null){
				map.put(arr[a],map.get(arr[a])+1);
			}
			else {
				map.put(arr[a],1);
			}
		}
		for (int i = 0; i <10 ; i++) {
			System.out.println(i + " -- 重復(fù)個數(shù)：" + map.get(i));
		}
	}
}

	public static void main (String[] args){
		Random random = new Random();
		int[] arr = new int[20];
		for (int i = 0; i < 20; i++) {
			arr[i] = random.nextInt(10);
			if (i < arr.length - 1) {
				System.out.print(arr[i]+"，");
			} else {
				System.out.print(arr[i] + "\r\n 結(jié)果：" + "\r\n" );
			}
		}
		// 輸出arr數(shù)組中重復(fù)元素，重復(fù)數(shù)量
		// 循環(huán)處理
		// cyclingDemo(arr);
		// map處理
		mapDemo(arr);
	}
}

package com.softsec.demo;
/**
 * 二分查找算法，兩種方法，一種遞歸一種非遞歸
 * @author chenhh
 *
 */
public class BinaryQry {
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		int[] arr = new int[] { 1, 20, 23, 24, 35, 46, 77, 78, 99, 100 };
		int index = search(arr,0,arr.length-1,78);
		//int index = search2(arr, 11);
		if (index == -1) {
			System.out.println("沒找到");
			return;
		}
		System.out.println("在數(shù)組的第" + (index+1) + "位");
	}
	/*
	 * 遞歸方法查找
	 */
	public static int search(int[] arr, int left, int right, int key) {
		if (left <= right) {
			int mid = (left + right) / 2;
			if (key < arr[mid]) {
				return search(arr, left, mid - 1, key);
			} else if (key > arr[mid]) {
				return search(arr, mid + 1, right, key);
			} else {
				return mid;
			}
		}
		return -1;
	}
	/*
	 * 非遞歸方法查找
	 */
	public static int search2(int[] arr, int key) {
		int left = 0;
		int right = arr.length - 1;
		int mid = 0;
		while (left <= right) {
			mid = (left + right) / 2;
			if (key == arr[mid]) {
				return mid;
			} else if (key > arr[mid]) {
				left = mid + 1;
			} else if (key < arr[mid]) {
				right = mid - 1;
			}
		}
		return -1;
	}
}

package com.softsec.demo;
/**
 * 兩個有序數(shù)組合并成一個有序數(shù)組的實現(xiàn)類
 * @author chenhh
 *
 */
public class ArrayMerge {
	/**
	* 數(shù)組合并方法
	* @param arrayM
	* @param arrayN
	* @return
	*/
	public static int[] mergeArray(int arrayM[],int arrayN[]){
		int newArray[];
		// 定義一個新數(shù)組，長度為兩個有序數(shù)組長度之和
		newArray = new int[arrayM.length + arrayN.length];
		// start:arrayM數(shù)組下標(biāo)    end：arrayN數(shù)組下標(biāo)  k：newArray新數(shù)組下標(biāo)
		int start=0,end=0,k=0;
		// 循環(huán)比較兩個數(shù)組，較小元素的放入新數(shù)組，較小元素所在數(shù)組下標(biāo)加一，較大元素對應(yīng)的數(shù)組下標(biāo)不加一，直到某一個下標(biāo)等于數(shù)組長度時退出循環(huán)
		while(start<arrayM.length && end<arrayN.length) {
			if(arrayM[start] <= arrayN[end]) {
				newArray[k++] = arrayM[start++];
			}else{
				newArray[k++] = arrayN[end++];
			}
		}
		/* 后面兩個while循環(huán)是用來保證兩個數(shù)組比較完之后剩下的一個數(shù)組里的元素能順利都放入新數(shù)組
		* 此時較短數(shù)組已經(jīng)全部放入新數(shù)組，較長數(shù)組還有部分剩余，最后將剩下的部分元素放入新數(shù)組，因為數(shù)組是有序，所以直接把剩下的順序加入即可*/
		while(start < arrayM.length) {
			newArray[k++] = arrayM[start++];
		}
		while(end < arrayN.length) {
			newArray[k++] = arrayN[end++];
		}
		return newArray;
	}
	/**
	* 數(shù)組打印方法
	* @param arr
	*/
	public static void print(int[] arr) {
		for(int i=0; i<arr.length;i++) {
			if (i < arr.length -1) {
				System.out.print(arr[i]+"，");
			} else {
				System.out.print(arr[i]);
			}
		}
	}
	public static void main(String[] args) {
		int[] arrayM = {1,3,5,7,8,9,14,16,21};
		int[] arrayN = {0,10,20,30,40,50};
		print(mergeArray(arrayM,arrayN));
	}
}