PHP 和 MYSQL 数据库连接和表创建仅一次（如果它尚不存在）？

CREATE DATABASE IF NOT EXISTS yourDatabaseName;

CREATE TABLE IF NOT EXISTS yourTableName
(
   yourColumnName yourDatatype,
   .
   .
   .
   N
);

Mysql> CREATE DATABASE IF NOT EXISTS login;
Query OK, 1 row affected (0.23 sec)

mysql> CREATE TABLE IF NOT EXISTS DemoTable
(
   Id int
);
Query OK, 0 rows affected (0.56 sec)