SQL Pattern Matching: Understanding LIKE Operator and Wildcards
Are you looking for specific data in your database but can’t seem to remember every detail? SQL pattern matching might be the solution you need.
SQL pattern matching allows you to search for data in a database by using predefined patterns. One of the most commonly used operators in SQL pattern matching is the LIKE operator, which enables users to search for text in a database’s columns by matching specific patterns.
In this article, we will discuss how to use the LIKE operator, wildcards, and pattern matching in SQL.
Syntax of LIKE Operator in SQL
The LIKE operator is used to search for data in a column that matches a specific pattern. The syntax for using the LIKE operator in SQL is as follows:
SELECT column1, column2, ...
FROM table_name
WHERE columnN LIKE pattern;In the code snippet above, ‘columnN’ refers to the name of a column in the table; ‘pattern’ refers to the specific pattern you want to search.
SQL Partial Match using Wildcards
Wildcards in SQL allow for partial matches. They enable users to search for data that matches specific patterns.
One of the most commonly used wildcards in SQL is the percent wildcard (%). Here are some examples of how you can use wildcards in SQL:
1. Searching for Substrings using the Percent Wildcard
In SQL, the percent symbol (%) wildcard is used to match any number of characters in a string. This makes it possible to search for substrings in a text field.
Here is an example:
SELECT *
FROM employees
WHERE first_name LIKE '%john%';The code snippet above searches for any employee with ‘john’ as part of their first name, regardless of whether it appears at the beginning, middle, or end of the field. 2.
2. Searching for Specific Characters using the Percent Wildcard
You can also use the percent wildcard to search for specific characters in a column. For instance, to get all the rows that start with ‘j’, type the following:
SELECT *
FROM employees
WHERE first_name LIKE 'j%';The code above searches for names that start with the letter ‘j.’ You can also search for last names that end with ‘son’ using a similar query:
SELECT *
FROM employees
WHERE last_name LIKE '%son';3. Combining Percent Wildcard with Other Wildcards
By combining wildcards in SQL, you can search for even more complex patterns.
For instance, to find an employee whose name begins with ‘j’ followed by any two characters and then ‘n,’ type this query:
SELECT *
FROM employees
WHERE first_name LIKE 'j__n%';Combining NOT and LIKE Operators
In some cases, you may be interested in searching for data that does not match a specific pattern. You can use the NOT operator to do this.
For instance, the query below searches for all employees whose name does not contain ‘john’:
SELECT *
FROM employees
WHERE first_name NOT LIKE '%john%';Using LIKE in other SQL Statements
The LIKE operator can also be used in other SQL statements such as UPDATE and DELETE. To update all employees with ‘john’ as part of their first name, use the following query:
UPDATE employees
SET department = 'Marketing'
WHERE first_name LIKE '%john%';To delete all employees with ‘john’ as part of their first name, type this query:
DELETE
FROM employees
WHERE first_name LIKE '%john%';Conclusion
Using the LIKE operator and wildcards in SQL provides a powerful and flexible way to search for data in databases. You can use percentage wildcards to search for partial matches, combine them with other wildcards to create more complex queries, and use NOT to exclude specific data.
With this knowledge, you can easily locate data you need from your database with minimum effort and time.
SQL Partial Match using Underscore Wildcard
In addition to the percent wildcard, SQL also has the underscore wildcard (_), which can be used to match single characters in a column’s value. In this section, we will explore how to use the underscore wildcard in SQL pattern matching.
Searching for a Specific Character using Underscore Wildcard
The underscore wildcard in SQL represents a single character. In other words, if you want to search for a specific character, you can use the underscore wildcard.
Here is an example of how to search for all employees whose first name starts with ‘J’ and has the second letter ‘o’:
SELECT *
FROM employees
WHERE first_name LIKE 'J_o%';The code above searches for names that have ‘J’ as the first letter of their first name, ‘o’ as the second letter, and any number of characters after that.
Searching for a Fixed Character Length using Underscore Wildcard
You can also use the underscore wildcard to search for a fixed length of characters. For example, to search for all employees whose last name has exactly five characters, enter the query below:
SELECT *
FROM employees
WHERE last_name LIKE '_____';The code above searches for any last name that has five characters.
Using Underscore Wildcard in the Middle of a Search String
You can also use the underscore wildcard in the middle of a search string to match any single character. Here is an example of how to search for employees whose first name contains ‘a’ as the second letter:
SELECT *
FROM employees
WHERE first_name LIKE '_a%';The code above matches any name that has ‘a’ as the second letter in their first name, regardless of the length of the first name.
Using LIKE in SQL with Other Operators
In addition to using LIKE as a standalone operator, you can use it with other operators to create more specific queries. Here are some examples:
Using LIKE and NOT LIKE with Other Operators
To find all employees whose first name starts with ‘J’ but does not have ‘ohn’ as the third, fourth, and fifth letters, enter the query below:
SELECT *
FROM employees
WHERE first_name LIKE 'J%'
AND first_name NOT LIKE 'Joh_n%';The code above searches for names with ‘J’ as the first letter of their first name and does not have ‘ohn’ as the third, fourth, and fifth letters.
Using LIKE in UPDATE and DELETE Statements
Besides SELECT statements, you can use the LIKE operator in UPDATE and DELETE statements to modify or delete specific data. Here is an example of how to update all employees whose last names start with ‘S’:
UPDATE employees
SET department = 'HR'
WHERE last_name LIKE 'S%';The code above updates the department of all the employees whose last name starts with the letter ‘S’ to HR. To delete all employees whose last names start with ‘T’, enter the query below:
DELETE
FROM employees
WHERE last_name LIKE 'T%';The code above deletes all employees whose last names start with the letter ‘T’.
Conclusion
SQL pattern matching allows you to search for data in a database by using predefined patterns. The LIKE operator, underscore wildcard, and percentage wildcard enable you to search for partial matches, specific characters, specific character length, or match any single character when searching for data.
Using LIKE with other operators such as NOT LIKE, UPDATE, and DELETE statements enhances your queries’ specificity, saving you time and effort. With these tools, you can navigate your database’s data with precision and ease.
Learning More about SQL Pattern Matching:
Introducing SQL Basics Course, Practice Set, and Practice Track
Learning SQL pattern matching is a useful skill for data analysts, developers, and anyone working with databases. Understanding how to use the LIKE operator and wildcards can help you retrieve data quickly and efficiently.
In this section, we will introduce you to some resources to help you learn SQL basics and practice SQL pattern matching skills.
Introducing SQL Basics Course
For beginners, the SQL Basics course on Khan Academy is an excellent place to start learning SQL. The course introduces you to the SQL language and how it is used to interact with databases.
You will learn how to use the SELECT statement to retrieve data, filter data using WHERE, aggregate data with GROUP BY, and join data from multiple tables. The course also introduces SQL pattern matching and how to use the LIKE operator and wildcards to search for specific patterns in your data.
You will learn about the underscore and percentage wildcards and their use in pattern matching. Once you complete the course, you will have a strong foundation in SQL basics, including pattern matching.
Trying SQL Practice Set
Once you’ve learned the basics of SQL pattern matching, it’s time to try your skills with a practice set. A practice set offers you a chance to apply your knowledge in a simulated environment.
It allows you to experiment and try different queries without the risk of affecting your live database.
W3Schools provides a comprehensive SQL Practice Set, testing your SQL skills with multiple-choice, multiple-select, and fill-in-the-blank questions.
The set covers a wide range of SQL concepts, from basic queries to advanced SQL statements. The practice set also has a SQL pattern matching section where you can practice SQL pattern matching with various examples.
SQL Practice Track
If you’re looking for an in-depth and comprehensive practice track to improve your SQL pattern matching skills, then the
SQL Practice Track on LeetCode may be the solution you need. LeetCode’s
SQL Practice Track provides up to 160 practice questions in which SQL pattern matching is applied.
On the
SQL Practice Track, you will receive problems designed to polish your SQL skills, with the opportunity to practice pattern matching. The site has a progress tracker to determine your mastery level and help target where you need to improve.
Even better, they have a leaderboard to keep you motivated and engage in friendly competition with others worldwide.
Conclusion
SQL pattern matching is an essential skill for data analysts, developers, and other professionals working with databases. Whether you are new to SQL or an experienced user, taking a course, practicing, or participating in a practice track can enhance your pattern matching skill set.
Learning SQL can facilitate modern-day work efficiency and data-driven decision making. There is no excuse not to join a practice set and practice track and enhance your SQL pattern matching skillset.
In conclusion, learning SQL pattern matching is crucial for professionals working with databases. Knowing how to use the LIKE operator and wildcards can help you retrieve data more quickly and efficiently.
Some resources that can help you learn SQL basics and practice SQL pattern matching skills include courses, practice sets, and practice tracks. Learning SQL can facilitate work efficiency and data-driven decision making.
By taking advantage of these resources, you can improve your SQL pattern matching skills and become more proficient in working with databases.