How to use database statements to modify the database name in PHP

In PHP development, we often need to modify the database name. Sometimes, we need to change the name of an existing database to another name. In this case, we need to use some specific PHP database statements to achieve this. This article will introduce how to use these statements to modify the database name.

Generally speaking, the database name is specified when the database is created and not modified when using it. However, in some cases, the database name needs to be modified. For example, you may need to distinguish a database in a production environment from a database in a test environment, or you may need to use the same database structure in different projects, but with different database names. Regardless of the reason, modifying the database name is a common task.

First, you need to connect to the database you want to modify. In PHP, use PDO or MySQLi for database connections. After this, you need to use the ALTER DATABASE statement to modify the database name. Specifically, use the following syntax:

ALTER DATABASE old_database_name RENAME TO new_database_name;

This statement changes old_database_name to new_database_name. Note that you need to have the appropriate permissions to perform this operation. Normally, only users with SUPER permissions can perform this operation.

If you do not want to use the ALTER DATABASE statement to modify the database name, there is another way to achieve this goal. You can create a new database in MySQL, copy all tables from the old database to the new database, and then delete the old database. Here are the basic steps to achieve this in PHP:

1. Create a stored procedure that contains all the tables you want to copy. This process will take the definitions of each table from the old database and create them in the new database.

   DELIMITER $$
   CREATE PROCEDURE `copy_all_tables`(IN old_db_name VARCHAR(255), IN new_db_name VARCHAR(255))
   BEGIN
     DECLARE done INT DEFAULT FALSE;
     DECLARE tbl_name VARCHAR(255);
     DECLARE cur CURSOR FOR SELECT table_name FROM information_schema.tables WHERE table_schema = old_db_name;
     DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;
   
     OPEN cur;
   
     read_loop: LOOP
    FETCH cur INTO tbl_name;
    IF done THEN
      LEAVE read_loop;
    END IF;
   
    SET @s = CONCAT('CREATE TABLE ', new_db_name, '.', tbl_name, ' LIKE ', old_db_name, '.', tbl_name);
    PREPARE stmt FROM @s;
    EXECUTE stmt;
    DEALLOCATE PREPARE stmt;
     END LOOP;
   
     CLOSE cur;
   END$$
   DELIMITER ;

2. Call the stored procedure to copy all tables from the old database to the new database.

CALL copy_all_tables('old_database_name', 'new_database_name');

3. Delete the old database.

DROP DATABASE old_database_name;

It should be noted that since the function involves security issues and the framework may maintain the structure by itself, please use this method with caution.

In summary, changing the database name is a relatively simple task. Using the ALTER DATABASE statement, you can change names quickly and easily. However, if you find that you are unable to use this statement, or need to use another method to accomplish this task, use the above code with caution. Either way, you need to think about the order of operations and understand all the steps in order to perform this task safely.

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