Ultimate Guide to SQL Patterns in Technical Interviews/

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Pattern Search

Pattern Search

Learn about the Pattern search pattern that filters rows based on partial text matches using flexible and efficient text-based tools.

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Sometimes, we need to find customers whose names start with “J,” products that include the word “phone,” or emails ending in “@example.com.” These are not exact matches; they require pattern matching, which is where this pattern comes into play. Whether it’s for filtering specific user behavior, parsing text inputs, or validating form fields, Pattern search is a practical and essential technique.

In this lesson, we’ll learn how to search within strings using SQL patterns, with tools like LIKE, ILIKE, wildcards, and REGEXP. We’ll also explore best practices for clarity and performance.

By the end of this lesson, we will be able to:

  • Understand how and when to use pattern-based filters in SQL.

  • Use LIKE, %, _, and regular expressions (REGEXP) to match text.

  • Identify common mistakes and performance pitfalls in pattern matching.

  • Apply pattern search to solve real-world text filtering problems.

Pattern overview

Category:

  • Filtering Patterns

Intent:

To retrieve rows based on partial matches in text fields by using pattern matching techniques such as LIKE or regular expressions.

Motivation:

In real-world databases, we often need to find partial or fuzzy matches, such as emails containing a domain, product names that include a brand, or phone numbers in a specific format. Pattern search allows us to flexibly filter rows without relying on exact equality.

Also known as

  • Text match

  • Wildcard filter

  • Regex match

Structure

There are two main ways we structure pattern searches:

  1. Basic wildcard matching using LIKE and ILIKE:

    1. % for any number of characters.

    2. _ for a single character.

SELECT column1, column2, ...
FROM   table_name
WHERE  column_name LIKE 'pattern';
Syntax of Pattern search pattern using the wildcards

  1. Advanced matching using REGEXP or RLIKE:

    1. Allows full regular expressions for complex searches.

SELECT column1, column2, ...
FROM   table_name
WHERE  column_name REGEXP 'regex_pattern';
Syntax of Pattern search pattern using advanced matching

Keywords

LIKE, ILIKE, %, _, REGEXP, RLIKE, NOT LIKE, NOT REGEXP

Problem structure

We use the Pattern search pattern when:

  • We want to find values that match a specific text pattern or structure.

  • We’re searching within strings using wildcards, partial matches, or regular expressions.

  • We need to identify entries based on naming conventions, prefixes/suffixes, or embedded patterns.

  • We’re working with tools like LIKE, ILIKE, or REGEXP to define flexible match conditions.

  • Look for keywords like: “starts with,” “ends with,” “contains,” “matches pattern,” or “regular expression” to identify when this pattern ...