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Common situations of mysql index failure

PHP Chinese website brings to you common situations in which mysql indexes fail: 1. Using functions or operations; 2. Implicit type conversion; 3. Using not equal to (!= or <>); 4. Using the LIKE operator, and Starting with a wildcard; 5. OR condition; 6. NULL value; 7. Low index selectivity, etc.

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mysql mysql index Index failure implicit type conversion sql statement Poor index selection index

Table of Contents

Common situations of mysql index failure

Several situations of mysql index failure

Common situations: 1. Use functions or operations; 2. Implicit type conversion; 3. Use not equal to (!= or <>); 4. Use the LIKE operator and start with a wildcard; 5. OR conditions; 6. NULL Value; 7. Low index selectivity; 8. Leftmost prefix principle of composite index; 9. Optimizer decision; 10. FORCE INDEX and IGNORE INDEX.

Feb 21, 2024 pm 04:23 PM

mysql mysql index Index failure implicit type conversion

Situation causing MySQL index failure

Several situations of MySQL index failure and code examples Introduction: In the MySQL database, indexes are one of the important factors to improve query performance. However, sometimes we find that the index does not play the expected role, query performance is not improved, and even causes the query to become slower. The reason is probably that the index is invalid. This article will introduce several common situations that cause MySQL index failure and give corresponding code examples. 1. Use functions or expressions to perform operations on index columns. If the index columns are used in the query statement,

Feb 18, 2024 pm 06:02 PM

sql statement mysql index Poor index selection

How to solve MySQL index failure

1. Preface When performing an index query on a SQL statement, you will encounter an index failure, which has a crucial impact on the feasibility and performance efficiency of the statement. This article analyzes why the index fails and what situations will cause the index to fail. As well as optimization solutions for index failure, it focuses on the leftmost prefix matching principle, MySQL logical architecture and optimizer, index failure scenarios and why it fails. 2. The leftmost prefix matching principle. I have previously written an article about the characteristics and optimization issues of adding indexes to MySQL. The following will introduce the relevant content of index failure. First, introduce a principle that will be used in the subsequent causes of index failure: the leftmost prefix matching principle. The underlying principle of the leftmost prefix: when establishing a joint index in MySQL

Jun 04, 2023 am 09:24 AM

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15 Mysql index failure scenarios you deserve to know (helping you avoid pitfalls quickly)

This article summarizes and shares 15 Mysql index failure scenarios so that everyone can avoid pitfalls. I hope it can help everyone!

Mar 01, 2022 am 11:17 AM

mysql Index failure

What are the situations in which mysql index fails?

Index failure: 1. The like query starts with "%"; 2. The index is not used before and after the or statement; 3. The first column index is not used in the combined index; 4. "IS NULL" or "IS NULL" is used on the index column. IS NOT NULL" operation; 5. Use "not", "<>", "!=", etc. on the index field.

Jan 05, 2022 pm 03:46 PM

mysql Index failure

What should I do if the Mysql index fails? Brief analysis of failure reasons

This article will record a Mysql index failure and analyze the reasons for Mysql index failure. I hope it will be helpful to you!

Nov 02, 2021 am 11:28 AM

mysql index

Introducing the situation of mysql index failure

Indexes are a very important chapter for MySQL. There are also a lot of index knowledge points. If you want to master them thoroughly, you need to break down each knowledge point one by one. Today, let’s first talk about the situations that will cause index failure.

Nov 30, 2020 pm 05:52 PM

mysql index