通信录（数据库）

 这个感受比较简单些，由于直接调用sql语句就行了，我看着别人的代码理解了一遍，本身敲了一遍

参考 ----->    https://blog.csdn.net/jiaqi_327/article/details/20799277

#include <stdio.h>
#include <stdlib.h>
#include <sqlite3.h>

sqlite3 *db = NULL;

void welcome()
{
	printf("1.查看通信录\n");
	printf("2.增长联系人\n");
	printf("3.删除联系人\n");
	printf("4.修改联系人信息\n");
	printf("5.查找联系人\n");
}

static int callback(void * data, int argc, char * * argv, char * * name)
{
	int i;

	for(i = 0; i < argc; i++)
	{
		printf("%s = %s\n",name[i],argv[i] ? argv[i] : "NULL");
	}
	printf("\n");
	return 0;
}

void show()
{
	char *errmsg;
	char *sql = NULL;
	int ret;
	
	sql = "select * from contact;";
	ret = sqlite3_exec(db,sql,callback,NULL,&errmsg);
	if(ret != SQLITE_OK)
	{
		printf("显示失败!%s\n",errmsg);
		sqlite3_free(errmsg);
	}
}

void add()
{
	char *errmsg = 0;
	char *sql = NULL;
	int ret;
	char *name;
	char *age;
	char *relation;
	char *number;

	name = (char *)malloc(sizeof(char)*10);
	age = (char *)malloc(sizeof(char)*11);
	relation = (char *)malloc(sizeof(char)*10);
	number = (char *)malloc(sizeof(char)*11);
	sql = (char *)malloc(sizeof(char)*100);

	printf("请输入联系人的姓名：\n");
	scanf("%s",name);
	printf("请输入联系人的年龄：\n");
	scanf("%s",age);
	printf("请输入与联系人的关系：\n");
	scanf("%s",relation);
	printf("请输入联系人的电话：\n");
	scanf("%s",number);

	sprintf(sql,"insert into contact values('%s','%s','%s','%s');",name,age,relation,number);
	ret = sqlite3_exec(db,sql,NULL,NULL,&errmsg);
	if(ret != SQLITE_OK)
	{
		printf("添加失败!%s",errmsg);
		sqlite3_free(errmsg);
	}

	free(name);
	free(relation);
	free(number);
	free(sql);
}

void delete()
{
	char *errmsg = 0;
	char *sql = NULL;
	int ret;
	char *name;

	name = (char *)malloc(sizeof(char)*10);
	sql = (char *)malloc(sizeof(char)*64);

	printf("请输入你要删除的联系人：");
	scanf("%s",name);

	sprintf(sql,"delete from contact where name ='%s'",name);
	ret = sqlite3_exec(db,sql,NULL,NULL,&errmsg);
	if(ret != SQLITE_OK)
	{
		printf("删除失败！%s\n",errmsg);
		sqlite3_free(errmsg);
	}

	free(name);
	free(sql);
}

void update()
{
	char *errmsg;
	char *sql = NULL;
	int ret;
	char *name;
	char *number;

	name = (char *)malloc(sizeof(char)*10);
	number = (char *)malloc(sizeof(char)*11);
	sql = (char *)malloc(sizeof(char)*64);

	printf("请输入你要修改的联系人姓名：");
	scanf("%s",name);

	printf("请输入你修改的电话号码:");
	scanf("%s",number);

	sprintf(sql,"update contact set number = '%s' where name = '%s'",number,name);
	ret = sqlite3_exec(db,sql,NULL,NULL,&errmsg);
	if(ret != SQLITE_OK)
	{
		printf("修改失败!%s\n",errmsg);
		sqlite3_free(errmsg);
	}

	free(name);
	free(number);
	free(sql);	
}

void search()
{
	char *errmsg;
	char *name;
	char *sql;
	int ret;

	printf("请输入你要查询的联系人的名字!\n");
	scanf("%s",name);

	name = (char *)malloc(sizeof(char)*10);
	sql = (char *)malloc(sizeof(char)*64);

	sprintf(sql,"select * from contact where name = '%s'",name);
	ret = sqlite3_exec(db,sql,callback,NULL,&errmsg);
	if(ret != SQLITE_OK)
	{
		printf("查询失败!%s\n",errmsg);
		sqlite3_free(errmsg);
	}

	free(name);
	free(sql);
	
}


int main(void)
{
	char *errmsg;
	int ret;
	int num;
	char *sql= NULL;
	
	ret = sqlite3_open("contact.db",&db);
	if(ret)
	{
		printf("不能打开数据库!%s\n",sqlite3_errmsg(db));
		return -1;
	}

	sql = (char*)malloc(sizeof(char)*64);
	
	sql = "create table contact(name text,age text,relation text,number text);";
	ret = sqlite3_exec(db,sql,NULL,NULL,&errmsg);
	if(ret != SQLITE_OK)
	{
		printf("表已经存在!\n");
	}

	do
	{
		welcome();
		printf("请输入序号:");
		scanf("%d",&num);
		
		switch (num)
		{
			case 1:show();break;
			case 2:add();break;
			case 3:delete();break;
			case 4:update();break;
			case 5:search();break;
		}			
	}while(num);

	return 0;
}