Shulou(Shulou.com)05/31 Report--

This article introduces the relevant knowledge of "how to optimize MySQL database performance". In the operation process of actual cases, many people will encounter such difficulties. Next, let Xiaobian lead you to learn how to deal with these situations! I hope you can read carefully and learn something!

MySQL performance optimization is the only way for MySQL database development, MySQL database performance optimization is also the witness of MySQL database progress, the following will be from four aspects of MySQL database performance optimization methods.

1. Select the most applicable field attributes

MySQL works well for large data volumes, but in general, the smaller the table in the database, the faster queries will be executed on it. Therefore, when creating a table, we can set the width of the fields in the table as small as possible for better performance. For example, when defining the field ZIP Code, if you set it to CHAR(255), you obviously add unnecessary space to the database, and even using VARCHAR is redundant, because CHAR(6) can do the job well. Similarly, we should use MEDIUMINT instead of BIGIN to define integer fields if possible.

Another way to improve efficiency is to set fields to NOT NULL whenever possible, so that the database does not have to compare NULL values in future queries.

For some text fields, such as "province" or "gender," we can define them as ENUM types. Because ENUM types are treated as numeric data in MySQL, numeric data is processed much faster than text types. In this way, we can improve the performance of the database.

Use JOIN instead of Sub-queries

MySQL has supported SQL subqueries since 4.1. This technique uses SELECT statements to create a single-column query result, which can then be used as a filter condition in another query. For example, if we want to delete customers who do not have any orders in the customer basic information table, we can use the sub-query to extract all customer IDs that issue orders from the sales information table, and then pass the results to the main query, as shown below:

DELETE FROM customerinfo

WHERE CustomerID NOT in (SELECT CustomerID FROM salesinfo )

Using subqueries allows you to complete many SQL operations that logically require multiple steps at once, avoid transaction or table locks, and are easy to write. However, there are cases where subqueries can be joined more efficiently. Substitution. For example, suppose we want to extract all users who do not have an order record, we can do this with the following query:

SELECT * FROM customerinfo

WHERE CustomerID NOT in (SELECT CustomerID FROM salesinfo )

If JOIN is used.. to complete this query, much faster. Especially if there is an index on CustomerID in the salesinfo table, the performance will be better. The query is as follows:

SELECT * FROM customerinfo

LEFT JOIN salesinfoON customerinfo.CustomerID=salesinfo.

CustomerID

WHERE salesinfo.CustomerID IS NULL

JOIN.. It's more efficient because MySQL doesn't need to create temporary tables in memory to complete this logical two-step query.

Use union instead of manually created temporary tables

MySQL has supported UNION queries since version 4.0, which combines two or more SELECT queries that require temporary tables into one query. Temporary tables are automatically deleted at the end of the client query session, thus keeping the database clean and efficient. When using UNION to create a query, we only need to use UNION as a keyword to connect multiple SELECT statements. It is important to note that the number of fields in all SELECT statements should be the same. The following example demonstrates a query using UNION.

SELECT Name, Phone FROM client

UNION

SELECT Name, BirthDate FROM author

UNION

SELECT Name, Supplier FROM product

4. Business

Although we can use Sub-Queries, JOINs, and UNION to create a wide variety of queries, not all database operations can be done with one or a few SQL statements. More often than not, a series of sentences are needed to accomplish some kind of work. But in this case, when one of the statements in the block fails, the operation of the entire block becomes uncertain. Imagine inserting a piece of data into two associated tables at the same time. There may be such a situation: after a successful update in the first table, an unexpected situation occurs in the database, causing the operation in the second table not to be completed. This will cause incomplete data and even destroy the data in the database. To avoid this, you should use transactions, which either succeed or fail every statement in the statement block. In other words, the consistency and integrity of the data in the database can be maintained. Things begin with the BEGIN keyword and end with the COMMIT keyword. If an SQL operation fails in between, ROLLBACK restores the database to the state it was in before BEGIN began.

BEGIN;

INSERT INTO salesinfo SET CustomerID=14;

UPDATE inventory SET Quantity=11

WHERE item=book;

COMMIT;

Another important function of transactions is that when multiple users use the same data source at the same time, it can provide a secure access mode for users by locking the database, which can ensure that users 'operations are not interfered by other users.

"How to optimize MySQL database performance" content is introduced here, thank you for reading. If you want to know more about industry-related knowledge, you can pay attention to the website. Xiaobian will output more high-quality practical articles for everyone!

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.