What does hint mean in mysql

Hint in mysql is a special comment or syntax structure used to provide additional information or guidance to the query optimizer. It can be used in SQL query statements to affect the execution plan of the query or the behavior of the optimizer. , common Hints include: 1. STRAIGHT_JOIN, which forces the use of the table order specified in the connection order for connection operations; 2. IGNORE INDEX, instructs MySQL to ignore a certain index; 3. INDEX HINT, specifies to select an index among multiple indexes. Execute the query.

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

In MySQL, a hint is a special comment or syntax structure used to provide additional information or guidance to the query optimizer. They can be used in SQL query statements to affect the query's execution plan or the behavior of the optimizer.

Through Hint, we can provide some additional information to MySQL to help the optimizer generate a more efficient query plan. These hints can affect index selection, join order, join type, etc.

Common Hints in MySQL include:

1. STRAIGHT_JOIN: Force the use of the table order specified in the join order for join operations.

2. IGNORE INDEX: Instructs MySQL to ignore an index, that is, not to use the index to execute queries.
   

3. #INDEX HINT: Specify to select an index among multiple indexes to execute the query.

It should be noted that although Hint can provide additional optimization information, excessive or incorrect use of Hint may cause query performance degradation or produce incorrect query plans. Therefore, you should be careful when using Hint, and it is recommended to use it only when you really need to optimize query performance and have a deep understanding of database optimization.

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