Discuss the execution process of MySQL statements

MySQL is a popular relational database management system. Whether as a developer or administrator, it is very important to understand the execution process of MySQL. In this article, we will discuss the execution process of MySQL statements.

The execution process of MySQL statements can be divided into the following steps:

1. Lexical analysis

In MySQL, all SQL statements are composed of bytes composition. When the server receives SQL statements, it converts them into tokens through a program called a lexical analyzer.

For example, the following SQL statement:

SELECT * FROM mytable WHERE id = 1;

will be broken down into the following tokens:

SELECT, *, FROM, mytable, WHERE, id, =, 1, ;

2. Syntax analysis

Next, the MySQL server converts the tokens into executable queries. This process is called parsing. MySQL will verify whether the query is valid according to certain rules. If it is invalid, an error message will be returned to the client.

In the above example, the MySQL server will convert tokens into the following executable query:

SELECT all columns FROM mytable WHERE column id equals 1;

3. Optimizer

Before MySQL converts a query into executable instructions, it will be optimized through a program called the optimizer. The main goal of the MySQL optimizer is to make queries execute faster.

The work of the MySQL optimizer includes but is not limited to the following tasks:

• Determine appropriate indexes
• Rewrite subqueries
• Determine join tables The best sequence
• Determine the best query type

4. Executor

Finally, the MySQL server will execute the optimized query. This process is called an executor. It will execute the optimized query and return the results.

In the above example, the MySQL server will search all columns with an id value of 1 in mytable and return the results.

Summary

The execution process of MySQL includes lexical analysis, syntax analysis, optimizer and executor. Understanding the execution process of MySQL is very important for developers, because it can help them better utilize the functions of MySQL and formulate better query strategies.

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