Data key value processing skills in MySQL

MySQL is currently one of the most popular relational database management systems. As a MySQL developer, data key value processing is a problem we often encounter. In this article, I will share some commonly used MySQL data key value processing techniques, hoping to help everyone in actual development.

1. Use indexes to speed up queries

In MySQL, establishing appropriate indexes helps optimize query efficiency. Normally, we create indexes for commonly used query fields, such as primary keys, foreign keys, unique constraints, etc. In addition, when using BETWEEN, IN, LIKE and other conditions in the query, you can also perform index optimization on the fields that meet the conditions to improve query efficiency.

2. Avoid using fuzzy queries

In MySQL, when using the LIKE keyword for fuzzy matching, the query efficiency is usually low. Because MySQL needs to scan the entire table to find rows that meet the conditions, and when using wildcard characters, the more digits in the wildcard character, the slower the query speed will be. Therefore, in actual development, you should try to avoid using fuzzy queries, or use alternatives such as full-text search.

3. Use the JOIN keyword to connect tables

In MySQL, JOIN is a keyword that connects two or more tables. Normally, we use INNER JOIN to connect, and we can query all data that meets the association conditions between the two tables. In addition, if you need to query the data in the left table and display the situation when the right table is empty, you can use LEFT JOIN. If you need to query the data in the right table and display the situation when the left table is empty, you can use RIGHT JOIN.

4. Use the EXISTS keyword to query

In MySQL, EXISTS is a keyword used to determine whether a subquery returns results. When you need to query whether there is data in a related table in a table, you can use EXISTS to judge. In fact, EXISTS is more efficient than JOIN, because it only needs to determine whether the subquery returns results, while JOIN needs to connect two tables and then query.

5. Use CASE WHEN for conditional judgment

In MySQL, CASE WHEN is a convenient way to make conditional judgment. Through CASE WHEN, multiple IF statements or multiple query conditions can be combined into one statement, thereby reducing the complexity of the statement. For example, when different processing needs to be performed based on different conditions, you can use the CASE WHEN statement for judgment.

6. Query using subqueries

In MySQL, subquery is a way of nested query. It is usually used when the query result needs to be used as a condition or need for another query statement. Multiple inquiries. Through subqueries, complex query statements can be decomposed into multiple simple query statements to improve query efficiency. However, when using subqueries, you need to be careful to avoid multiple levels of nesting, otherwise it will have a greater impact on query speed.

In summary, there are many data key value processing techniques in MySQL, and you need to choose according to the specific situation. I hope this article can solve some problems for everyone in actual development and improve development efficiency and query efficiency.

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