MySQL WHERE IN чувствительный к регистру

Согласно документации MySQL, оператор WHERE в MySQL регистрозависимый по умолчанию. Это означает, что он различает заглавные и строчные буквы. Однако, вы можете изменить это поведение, используя указание COLLATE в выражении WHERE.

Давайте рассмотрим пример:

SELECT * 
FROM table_name 
WHERE column COLLATE utf8_general_ci IN ('Value1', 'value2');

В данном примере, мы используем COLLATE utf8_general_ci, которое указывает MySQL не учитывать регистр при сравнении значений в столбце с заданными значениями в операторе IN.

MySQL WHERE IN Case Sensitive

When working with MySQL, it is common to use the WHERE clause to filter query results based on certain conditions. The WHERE IN statement is used to specify multiple values in a single column to be included in the result set. However, the case sensitivity of the values in the WHERE IN clause can sometimes be a concern. This article will explain the behavior of the WHERE IN clause in MySQL with regard to case sensitivity and provide code examples to demonstrate the concept.

Understanding Case Sensitivity in MySQL

MySQL, by default, treats string comparisons as case-insensitive. This means that when comparing strings, MySQL ignores the case and treats uppercase and lowercase characters as equal. For example, the following query will return matching records regardless of whether the values in the column_name are in uppercase or lowercase:

SELECT * FROM table_name WHERE column_name = 'value';

However, this case-insensitive behavior does not apply to all aspects of MySQL, including the WHERE IN clause. When using the WHERE IN clause, MySQL treats string comparisons as case-sensitive by default. This means that the case of the values specified in the WHERE IN clause must match exactly with the case of the values stored in the column.

Case Sensitivity in WHERE IN Clause Example

To illustrate the case sensitivity in the WHERE IN clause, let's consider the following example:

Suppose we have a table called employees with a column named name, which stores the names of the employees. We want to retrieve the records of employees whose names are either "John" or "jane".

SELECT * FROM employees WHERE name IN ('John', 'jane');

In this case, the query will only return the records where the value in the name column is exactly "John" or "jane", taking into account the case sensitivity. If there are records with names like "john" or "Jane", they will not be included in the result set.

Case Insensitive Comparison in WHERE IN Clause

If you want to perform a case-insensitive comparison in the WHERE IN clause, you can use the COLLATE keyword along with a case-insensitive collation. A collation defines the rules for comparing and sorting characters in a character set. By using a case-insensitive collation, you can make the comparison case-insensitive.

SELECT * FROM employees WHERE name COLLATE utf8_general_ci IN ('John', 'jane');

In this example, the utf8_general_ci collation is used, which stands for "utf8 - Unicode for multilingual support, general - case-insensitive, ci - case-insensitive." The comparison will now be case-insensitive, and the query will return the records with names that match "John", "jane", "john", or "Jane".

Conclusion

In conclusion, when using the WHERE IN clause in MySQL, string comparisons are case-sensitive by default. This means that the values specified in the WHERE IN clause must match exactly with the case of the values stored in the column. However, you can perform a case-insensitive comparison by using a case-insensitive collation with the COLLATE keyword. With this knowledge, you can effectively filter query results using the WHERE IN clause while considering the case sensitivity of the values.