How to Use Wildcard Operators in SQL

SQL is a powerful tool for managing large amounts of data. It allows you to retrieve, insert, update, and delete data from databases. One of the most useful features of SQL is the ability to use wildcard operators to search for data. This article will explain what wildcard operators are, the different types of wildcard operators, and how to use them in SQL.

What are Wildcard Operators?

In SQL, a wildcard operator is a special character that can be used to represent one or more characters in a string of text. Wildcard operators are used in SQL statements that involve searching for data in the database. They allow you to specify part of a text string that you want to match, without having to specify the exact text.

There are two main types of wildcard operators used in SQL: the percent sign (%) and the underscore (_).

The Percent Sign (%)

The percent sign (%) is the most commonly used wildcard operator in SQL. It represents zero or more characters. For example, suppose you want to search for all the customers in your database whose names start with the letter “J”. You can use the following SQL statement:

SELECT *
FROM customers
WHERE customer_name LIKE 'J%';

The SQL statement selects all the rows from the customers table where the customer_name column starts with the letter “J”. The percent sign (%) represents zero or more characters that can follow the letter “J”.

Another example is if you want to search for all the customers in your database whose names contain the word “John”. You can use the following SQL statement:

SELECT *
FROM customers
WHERE customer_name LIKE '%John%';

The SQL statement selects all the rows from the customers table where the customer_name column contains the word “John”. The percent sign (%) represents zero or more characters that can appear before and after the word “John”.

The Underscore (_)

The underscore (_) is another wildcard operator used in SQL. It represents a single character. For example, suppose you want to search for all the customers in your database whose names start with the letter “J” and have a second letter that is “o”. You can use the following SQL statement:

SELECT *
FROM customers
WHERE customer_name LIKE 'J_o%';

The SQL statement selects all the rows from the customers table where the customer_name column starts with the letter “J”, followed by any single character, then the letter “o”, and zero or more characters after that.

Using Wildcard Operators in SQL Statements

Wildcard operators can be used in SQL statements that involve searching for data in the database. The most common SQL statement that uses wildcard operators is the SELECT statement.

The SELECT Statement

The SELECT statement is used to retrieve data from one or more tables in a database. Wildcard operators can be used in the WHERE clause of the SELECT statement to search for data that matches a specific pattern. For example, suppose you want to search for all the customers in your database who live in a city that starts with the letter “N”. You can use the following SQL statement:

SELECT *
FROM customers
WHERE customer_city LIKE 'N%';

The SQL statement selects all the rows from the customers table where the customer_city column starts with the letter “N”.

The INSERT Statement

The INSERT statement is used to add new data to a table in a database. Wildcard operators cannot be used in the INSERT statement.

The UPDATE Statement

The UPDATE statement is used to modify existing data in a table in a database. Wildcard operators can be used in the WHERE clause of the UPDATE statement to search for data that matches a specific pattern. For example, suppose you want to update the email addresses of all the customers in your database whose last names start with the letter “S”. You can use the following SQL statement:

UPDATE customers
SET customer_email = 'new_email@example.com'
WHERE customer_last_name LIKE 'S%';

The SQL statement updates the customer_email column for all the rows in the customers table where the customer_last_name column starts with the letter “S”.

The DELETE Statement

The DELETE statement is used to remove data from a table in a database. Wildcard operators can be used in the WHERE clause of the DELETE statement to search for data that matches a specific pattern. For example, suppose you want to delete all the customers in your database whose first names start with the letter “A”. You can use the following SQL statement:

DELETE FROM customers
WHERE customer_first_name LIKE 'A%';

The SQL statement deletes all the rows from the customers table where the customer_first_name column starts with the letter “A”.

Frequently Asked Questions

Conclusion

Wildcard operators are a powerful tool for searching for data in SQL. The percent sign (%) and the underscore () are the most commonly used wildcard operators in SQL. The percent sign (%) represents zero or more characters, while the underscore () represents a single character. Wildcard operators can be used in the WHERE clause of SQL statements such as SELECT, UPDATE, and DELETE. By using these operators, you can search for data that matches a specific pattern without having to specify the exact text.

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