SQL Wildcards are special characters that are used in SQL queries to match one or more characters in a string. They are used in conjunction with the LIKE operator to search for patterns in data. Wildcards are very useful when you need to search for data that matches a certain pattern, but you don't know the exact value of the data.
There are three types of SQL Wildcards:
The % wildcard is used to match any string of zero or more characters. For example, if you want to find all the names that start with the letter "J", you can use the following SQL query:
SELECT * FROM customers WHERE name LIKE 'J%';
This query will return all the customers whose name starts with the letter "J".
The _ wildcard is used to match any single character. For example, if you want to find all the names that have exactly four characters, you can use the following SQL query:
SELECT * FROM customers WHERE name LIKE '____';
This query will return all the customers whose name has exactly four characters.
The [ ] wildcard is used to match any single character within the specified range or set. For example, if you want to find all the names that start with the letter "J" or "K", you can use the following SQL query:
SELECT * FROM customers WHERE name LIKE '[JK]%';
This query will return all the customers whose name starts with the letter "J" or "K".
You can also use the [ ] wildcard to match any single character within a range of characters. For example, if you want to find all the names that have a vowel as the second letter, you can use the following SQL query:
SELECT * FROM customers WHERE name LIKE '_[aeiou]%';
This query will return all the customers whose name has a vowel as the second letter.
SQL Wildcards are very useful when you need to search for data that matches a certain pattern. They allow you to search for data without knowing the exact value of the data. By using the %, _, and [ ] wildcards, you can create powerful SQL queries that can search for data in a variety of ways.