What are the uses of mysql wildcards?

Mysql wildcard usage includes percent sign (%) and underscore (_). Detailed introduction: 1. The wildcard percent sign (%) can query data starting with a specific character, query data ending with a specific character, and query data containing specific characters; 2. Underscore (_) can query the second character as a specific character. Character data, query the data when the third character is a specific character, query the data when the fourth character is a specific character.

MySQL is a widely used relational database management system that provides many powerful functions and syntax for processing data. One of them is the use of wildcards, which are special characters used to match patterns in queries. Commonly used wildcard characters in MySQL include the wildcard percent sign (%) and underscore (_). This article will introduce the usage and examples of MySQL wildcards.

1. Wildcard percent sign (%):

The wildcard percent sign (%) is used to match characters of any length. It can appear anywhere in the pattern, meaning it matches any character or sequence of characters. Here are some examples of using the percent wildcard character:

- Query for data starting with a specific character:

SELECT * FROM table_name WHERE column_name LIKE 'abc%';

This query will return all data starting with 'abc', such as 'abc123', 'abcdef', etc.

- Query data ending with specific characters:

SELECT * FROM table_name WHERE column_name LIKE '%xyz';

This query will return all data ending with 'xyz' Data, such as '123xyz', 'abcdefxyz', etc.

- Query data containing specific characters:

SELECT * FROM table_name WHERE column_name LIKE '�c%';

This query will return all data containing 'abc' , such as 'abc123', 'abcdef', '123abc', etc.

2. Underscore (_):

Underscore (_) wildcard is used to match a single character. It can appear anywhere in the pattern, meaning it matches any single character. Here are some examples of using the underscore wildcard character:

- Query data where the second character is a specific character:

SELECT * FROM table_name WHERE column_name LIKE '_b%';

This query will return all data whose second character is 'b', such as 'abc', 'bce', etc.

- Query data whose third character is a specific character:

SELECT * FROM table_name WHERE column_name LIKE '__c%';

This query will return the third character All data of 'c', such as 'abc', '123cde', etc.

- Query data whose fourth character is a specific character:

SELECT * FROM table_name WHERE column_name LIKE '___d%';

This query will return the fourth character All data of 'd', such as 'abcd', '1234def', etc.

It should be noted that the use of wildcards may lead to reduced query efficiency, especially in large databases. Therefore, when using wildcards, you should try to avoid using wildcards at the beginning of the pattern to improve query performance.

Summary:

MySQL’s wildcard percent sign (%) and underscore (_) are very useful tools that can help us match patterns in queries. By flexibly using wildcards, we can filter and search data more easily. However, it should be noted that when using wildcards, attention should be paid to query performance issues to avoid unnecessary performance losses. .

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