一.MySQl表的创建与删除
创建语句与删除语句
注意：
主键的数据类型，不可以是变长度类型需要()限制长度，表名字需要使用``符号来包围。
二.MySQl数据插入
三.MySQl数据删除
四.MySQl数据更新
使用语句
SET SQL_SAFE_UPDATES = 0;
show variables like 'SQL_SAFE_UPDATES';
当要哦
第一次修改后:
第二次修改后：
注意：WHERE里面可以使用AND以外，还可以使用OR，来合并多个条件，形成一个更为复杂的条件。
五 .MYSQL数据查询
附录：代码
cpp
#include <iostream>
#include <mysql.h>
void show_result(MYSQL_RES* result) {
//获取结果集列的数量
unsigned nFiles = mysql_num_fields(result);
//获取结果集行的数量
my_ulonglong nRows = mysql_num_rows(result);
//获取每一列的定义接口：
MYSQL_FIELD* fields = mysql_fetch_fields(result);
for (unsigned i = 0; i < nRows; i++) { //遍历每一行
MYSQL_ROW row = mysql_fetch_row(result);
//获取每一行结果
if (row != NULL) {
for (unsigned j = 0; j < nFiles; j++) {
//对于每一行遍历每列的信息
std::cout << "type:" << fields[j].type << " " << fields[j].name << " : " << row[j] << std::endl; //对应存储数据的值
}
}
std::cout << "==================" << std::endl;
}
}
int creat_user(MYSQL* pDB){ //创建新用户
std::string sql = "CREATE USER 'fc'@'localhost' IDENTIFIED BY ''";
int ret = mysql_real_query(pDB, sql.c_str(), (unsigned long)sql.size());
if (ret != 0) {
std::cout << "mysql error:" << mysql_error(pDB) << std::endl;
return -1;
}
return 0;
}
int grant_userpower(MYSQL* pDB) { //授予用户权限
std::string sql = "GRANT ALL PRIVILEGES ON *.* TO 'fc'@'localhost' with grant option";
int ret = mysql_real_query(pDB, sql.c_str(), (unsigned long)sql.size());
if (ret != 0) {
std::cout << "mysql error:" << mysql_error(pDB) << std::endl;
return -1;
}
return 0;
}
int creat_database(MYSQL* pDB) { //创建数据仓库
std::string sql = "CREATE DATABASE hello";
int ret = mysql_real_query(pDB, sql.c_str(), (unsigned long)sql.size());
if (ret != 0) {
std::cout << "mysql error:" << mysql_error(pDB) << std::endl;
return -1;
}
return 0;
}
int use_database(MYSQL* pDB) { //选择数据仓库
std::string sql = "use hello;";
int ret = mysql_real_query(pDB, sql.c_str(), (unsigned long)sql.size());
if (ret != 0) {
std::cout << "mysql error:" << mysql_error(pDB) << std::endl;
return -1;
}
return 0;
}
int grant_database_power(MYSQL* pDB) { //授予仓库权限
std::string sql = "GRANT ALL ON hello.* TO 'fc'@'localhost'";
int ret = mysql_real_query(pDB, sql.c_str(), (unsigned long)sql.size());
if (ret != 0) {
std::cout << "mysql error:" << mysql_error(pDB) << std::endl;
return -1;
}
return 0;
}
int create_table(MYSQL* pDB) { //创建数据库的表
std::string sql = "CREATE TABLE IF NOT EXISTS `hello` (`num` char(16) PRIMARY KEY)engine=InnoDB default charset=UTF8MB4;";
int ret = mysql_real_query(pDB, sql.c_str(), (unsigned long)sql.size());
if (ret != 0) {
std::cout << "mysql error:" << mysql_error(pDB) << std::endl;
return -1;
}
return 0;
}
int insert_data(MYSQL* pDB) { //插入数据库数据
std::string sql = "insert into `hello` (`编号`) values (\"9527\");";
int ret = mysql_real_query(pDB, sql.c_str(), (unsigned long)sql.size());
if (ret != 0) {
std::cout << "mysql error:" << mysql_error(pDB) << std::endl;
return -1;
}
return 0;
}
int delete_data(MYSQL* pDB) { //删除所筛选的数据
std::string sql = "delete from `hello` where `编号`=\"9527\";";
int ret = mysql_real_query(pDB, sql.c_str(), (unsigned long)sql.size());
if (ret != 0) {
std::cout << "mysql error:" << mysql_error(pDB) << std::endl;
return -1;
}
return 0;
}
int up_data(MYSQL* pDB) { //修改所筛选的数据
std::string sql = "update `hello` set age=30 where `编号`=\"9527\";";
int ret = mysql_real_query(pDB, sql.c_str(), (unsigned long)sql.size());
if (ret != 0) {
std::cout << "mysql error:" << mysql_error(pDB) << std::endl;
return -1;
}
return 0;
}
int make_query(MYSQL* pDB) { //查询数据库中的数值
std::string sql = "select * from `hello`;";
int ret = mysql_real_query(pDB, sql.c_str(), (unsigned long)sql.size());
if (ret != 0) {
std::cout << "mysql error:" << mysql_error(pDB) << std::endl;
return -1;
}
MYSQL_RES* result = mysql_store_result(pDB);
if (result != NULL) {
show_result(result); //展示数据
mysql_free_result(result); //释放结果,与use_result相互对应
}
return 0;
}
int fe() {
setlocale(LC_ALL, "en_GB.UTF-8"); //设置控制台编码
MYSQL* mysql = new MYSQL();
MYSQL* pDB = mysql_init(mysql); //初始化mysql对象
//这里两个变量 mysql和pDB 两个变量记录（指向）同一个值避免初始化失败后返回NULL指针内存泄漏的风险
if (pDB == NULL) {
std::cout << "mysql_init failed!" << std::endl;
return -1;
}
pDB = mysql_real_connect(pDB, "localhost", "root", "1234", "mysql", 3306, NULL, 0);
//连接数据库
std::cout << pDB << std::endl;
if (pDB) {
//creat_user(pDB);
//grant_userpower(pDB);
//creat_database(pDB);
//grant_database_power(pDB);
//获取SQL的数据
//use_database(pDB);
//make_query(pDB);
}
mysql_close(pDB);
delete(mysql);
return 0;
}
int main()
{
fe();
return 0;
}