Shulou(Shulou.com)06/01 Report--

This article mainly introduces how to use Union to optimize Like statements in MySQL, which has a certain reference value, interested friends can refer to, I hope you can learn a lot after reading this article, let the editor take you to understand it.

Optimizing Like statements with Union

1) sometimes, you may need to use the or operator in your query for comparison. When the or keyword is used too frequently in the where clause, it may cause the MySQL optimizer to mistakenly choose a full table scan to retrieve records. The union clause can make queries execute faster, especially if one query has an optimized index and the other query has an optimized index.

For example, if an index exists on first_name and last_name respectively, execute the following query statement:

Mysql > select * from students where first_name like 'Ade%' or last_name like' Ade%'

The above query is much slower than the following query that uses union to merge two query statements that make full use of the query.

Mysql > select * from students where first_name like 'Ade%' union all select * from students wherelast_name like' Ade%' Thank you for reading this article carefully. I hope the article "how to use Union to optimize Like sentences in MySQL" shared by the editor will be helpful to you. At the same time, I also hope you will support us and pay attention to the industry information channel. More related knowledge is waiting for you to learn!

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.