What are the several methods of database optimization?

Database optimization methods: 1. Select the most applicable field attributes; 2. Use connections to replace subqueries; 3. Use unions to replace manually created temporary tables; 4. Transactions; 5. Lock tables; 6. Use foreign keys.

#The operating environment of this article: Windows 7 system, Dell G3 computer.

Methods for database optimization:

The first method: Select the most applicable field attributes. MySQL can support the access of large amounts of data, but the smaller the table in the database, the faster the queries executed on it. Therefore, the field width in the table can be set as small as possible. The figure shows an example of this method.

Second method: Use connections instead of sub-queries (Sub-Queries). You can use the SELECT statement to create a single column of query results, and then use this result as a filter condition in another query. The figure shows an example of this method.

The third method: Use union (UNION) to replace the manually created temporary table. MySQL can combine two or more select queries that require the use of temporary tables into one query. The figure shows an example of this method.

The fourth method: Transaction. Not all database operations can be completed with only one or a few SQL statements. More often, a series of statements are needed to complete a certain kind of work. The integrity and consistency of data in the database can be maintained. The figure shows an example of this method.

Fifth method: Lock the table. Since the database will be locked during the execution of the transaction, other user requests can only wait until the transaction ends. In some cases we can get better performance by enlarging the lock table. The figure shows an example of this method.

The sixth method: Use foreign keys. The method of locking the table can protect the integrity of the data, but it cannot guarantee the relevance of the data. At this point we can use foreign keys. The figure shows an example of this method.

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