When does mysql create a temporary table?

Temporary tables in MySQL are created under the following circumstances: 1. When a statement containing "CREATE TEMPORARY TABLE" is executed, a temporary table will be created, which only exists in the current database connection, and after the connection is closed It will be automatically deleted; 2. When performing some complex queries or sorting operations, MySQL may automatically create temporary tables internally to store intermediate results.

Operating system for this tutorial: Windows 10 system, MySQL 8 version, Dell G3 computer.

In MySQL, temporary tables are created and used in specific scenarios.

Temporary tables are created under the following circumstances:

• When a statement containing CREATE TEMPORARY TABLE is executed, a temporary table is created. This temporary table only exists in the current database connection (session) and will be automatically deleted after the connection is closed.

• When performing some complex queries or sorting operations, MySQL may automatically create temporary tables internally to store intermediate results.

The main functions of temporary tables are as follows:

1. Storing intermediate results: Temporary tables can be used to store intermediate results during the query process. , especially when performing complex queries, multi-table joins, or sorting with large amounts of data. By saving intermediate state in temporary tables, you can make queries more efficient and avoid frequent calculations and reading of large data sets.

2. Decompose complex tasks: For tasks such as complex queries, data analysis, or report generation, large tasks can be split into multiple steps, and each step uses temporary tables to store and process data. , to simplify task logic and improve execution efficiency.

3. Reuse query logic: If a certain query logic needs to be used multiple times, you can encapsulate it into a temporary table and then reuse the temporary table in subsequent queries to avoid repeated calculations. and simplify query statements.

It should be noted that the temporary table is only valid in the current database connection (session), and will be automatically deleted after the connection is closed, and will not be persisted to disk. This means that the temporary table needs to be re-created every time a new connection is created. In addition, the naming of temporary tables must also follow certain rules to distinguish them from other tables.

In short, temporary tables can improve query performance, simplify complex tasks and reuse query logic in MySQL, providing a flexible and efficient way for data processing and query operations.

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