Filtering Data with the LIKE Operator and Wildcards

Kedeisha June 16, 2023

Filtering Data with the LIKE Operator and Wildcards

In this lesson, we will explore the LIKE operator and wildcard patterns for flexible data filtering. The LIKE operator allows us to perform pattern matching within a string column to retrieve data that matches a specific pattern. Understanding how to use wildcard characters in conjunction with the LIKE operator expands our filtering capabilities in SQL queries.

Understanding the LIKE Operator for Pattern Matching

The LIKE operator is used to perform pattern matching within a string column. It allows us to search for specific patterns or substrings within the values of a column. The general syntax for using the LIKE operator is as follows:

				
					SELECT 
    column1, 
    column2, 
FROM table_name
WHERE column LIKE 'pattern';

In the above syntax, “column” represents the column on which pattern matching is performed, and “pattern” specifies the pattern or substring we want to match.

Using Wildcard Characters

Wildcard characters are special symbols used in conjunction with the LIKE operator to match patterns in SQL. The two commonly used wildcard characters are:

% (Percent sign wildcard): It matches any sequence of characters (including zero characters). For example, ‘a%’ matches any value starting with ‘a’, such as ‘apple’, ‘ant’, or ‘aardvark’.
_ (Underscore wildcard): It matches any single character. For example, ‘b_’ matches any value with ‘b’ as the first character, followed by any single character, such as ‘ba’, ‘be’, or ‘bo’.

Applying Wildcard Matching for Flexible and Powerful Filtering

The combination of the LIKE operator and wildcard characters allows us to create flexible and powerful filtering conditions. We can use them to retrieve rows that match specific patterns or substrings within a column. Here are some examples:

Retrieving rows where the column starts with a specific substring:

				
					SELECT 
    column1, 
    column2, 
FROM table_name
WHERE column LIKE 'prefix%';

Retrieving rows where the column ends with a specific substring:

				
					SELECT 
    column1, 
    column2, 
FROM table_name
WHERE column LIKE '%suffix';

Retrieving rows where the column contains a specific substring:

				
					SELECT 
    column1, 
    column2, 
FROM table_name
WHERE column LIKE '%substring%';

Understanding the LIKE operator and wildcard characters (% and _) allows us to perform powerful pattern matching and flexible filtering in SQL queries. It expands our ability to search for specific patterns or substrings within string columns. In the next lesson, we will explore the IN and NOT IN operators for filtering data based on a list of values.