mysql table type modification

MySQL is an open source relational database management system. It provides a variety of table types to meet different needs. In practical applications, sometimes it is necessary to modify the table type. This article will introduce how to modify the type of MySQL table.

1. Overview

MySQL table types are mainly divided into InnoDB, MyISAM, MEMORY, CSV and other types. InnoDB is the default storage engine of MySQL. Each storage engine has its advantages and disadvantages, and it needs to be selected according to actual needs in actual applications.

In MySQL, modifying the data type of a table is generally divided into two situations:

1) Modify from a non-transactional table (such as MyISAM) to a transactional table (such as InnoDB);

2) Modify from transactional table (such as InnoDB) to non-transactional table (such as MyISAM).

The modification methods in the two situations are slightly different, and will be introduced in detail below.

2. Modify from non-transactional table to transactional table

Modifying non-transactional table to transactional table is a relatively common operation. The following describes how to modify a MyISAM table into an InnoDB table.

1) Check the type of the current table

You can use the DESCRIBE statement to check the basic information of the table, such as the table's field information, index information, etc. Execute the following command:

DESCRIBE tablename;

where tablename is the name of the table to be queried.

2) Back up data

Before modifying the type of the table, you need to back up the data in the table. You can use the mysqldump command to back up the data in the table to a file. For example, to back up the test_table table in the testDB library to the test_table.sql file, you can execute the following command:

mysqldump testDB test_table > test_table.sql

3) Lock table

Before modifying the table type, the table needs to be locked. In MySQL, a write lock is required to execute the ALTER TABLE statement. Therefore, before executing the ALTER TABLE statement, you need to lock the table to prevent other users from modifying the table.

You can lock the table through the following command:

LOCK TABLES tablename WRITE;

where tablename is the name of the table to be modified.

4) Modify the table type

Execute the following command to modify the table type from MyISAM to InnoDB:

ALTER TABLE tablename ENGINE=InnoDB;

Among them, tablename is the name of the table to be modified.

5) Unlock the table

After the modification is completed, the table needs to be unlocked. Execute the following command:

UNLOCK TABLES;

At this point, the MyISAM table is successfully modified into an InnoDB table.

3. Modification from transactional table to non-transactional table

In actual applications, modification from transactional table to non-transactional table is relatively rare. The following describes how to modify an InnoDB table to a MyISAM table.

1) Back up data

Before modifying the table type, you also need to back up the data in the table. The backup method is the same as before and will not be repeated here.

2) Create a new table

Because the storage methods of the two table types are different, the InnoDB table cannot be modified into a MyISAM table by directly modifying the table. Therefore, you need to create a new MyISAM table first and import data into the table.

You can create a new MyISAM table through the following command:

CREATE TABLE new_table
(

...

) ENGINE=MyISAM;

where, new_table is the name of the table to be created, ... is the field information and constraint information in the new table.

3) Import data into the new table

You can use the INSERT INTO statement to insert data from the original table into the new table. For example, to insert data from the test_table table into the new_table table, you can execute the following command:

INSERT INTO new_table SELECT * FROM test_table;

4) Rename the table

After the data import is completed, the new table needs to be renamed to the original table. You can execute the following command:

RENAME TABLE test_table TO old_table, new_table TO test_table;

where old_table is the old table name and test_table is the new table name.

At this point, the InnoDB table has been successfully modified into a MyISAM table.

4. Conclusion

Modifying the MySQL table type is a relatively common operation. In actual applications, different table types need to be selected based on actual needs. Whether it is modified from a non-transactional table to a transactional table or from a transactional table to a non-transactional table, table locking and data backup are required. This article introduces the basic methods of modifying MySQL table types, and hopes to be helpful to readers.

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