How to make case query in MySQL

In MySQL, query statements are a very basic and important operation. Query statements allow us to extract the data we need from the database and sort and filter it according to our needs. However, when actually using MySQL for data query, we often encounter many troubles and problems, including capitalization issues. Case in MySQL query statements is very sensitive, so we need to understand how to correctly perform case queries in MySQL.

The case problem in MySQL

The case problem in MySQL can be traced back to the design of the database. In MySQL, identifiers (such as table names, column names, variable names, etc.) are case-sensitive. This can cause us a lot of trouble in some cases.

For example, when we create a table, we specify a table name student. If we later use the SELECT statement to query the table, we cannot use Student or STUDENT and other similar case forms, otherwise the MySQL database will return error message.

How to query upper and lower case in MySQL

1. Use the BINARY keyword

When querying, use the BINARY keyword to make MySQL indistinguishable Upper and lower case. For example, we can use the following statement to query the student table:

SELECT * FROM student WHERE BINARY name = 'Tom';

In this way, MySQL will return the correct result regardless of the case of the name. Although this approach can solve the problem, using the BINARY keyword in a relatively large data set may affect the performance of the query, so the solution to the problem is not elegant.

2. Use the LOWER function

When making queries, another way to solve the case problem is to use MySQL's LOWER function. The LOWER function converts a string to lowercase letters. For example, we can use the following statement to query the student table:

SELECT * FROM student WHERE LOWER(name) = 'tom';

In this way, MySQL will convert all strings in the name field into lowercase, and then compare them with 'tom'. Using this approach, we can avoid the query performance impact of using the BINARY keyword.

Summary

The case problem in MySQL is a relatively simple but often overlooked problem. On the premise of ensuring the correctness and efficiency of the query, we should try to avoid using the BINARY keyword and try to use methods such as the LOWER function to solve the case problem.

In the actual development process, it is easy for us to ignore the case problem in MySQL, which may lead to some incorrect query results. Therefore, we need to carefully understand the case rules in MySQL and perform correct query operations based on the actual situation.

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