Contains SQL

How do I check if a string contains a specific substring in SQL?

The `LIKE` operator in SQL allows you to search for patterns within strings. The `CONTAINS` function, while not standard SQL, is available in some database systems. This helps find substrings within text fields.

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Description

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The `LIKE` operator is a fundamental tool for pattern matching in SQL. It's used to filter rows based on whether a column's value matches a specified pattern. Crucially, `LIKE` allows you to search for substrings. For example, you might want to find all customers whose names contain the substring 'Smith'. The `LIKE` operator uses wildcards, such as the percentage sign (%) to represent any sequence of characters and the underscore (_) to represent a single character. While the `CONTAINS` function is available in some database systems, it's not a standard SQL function. Its use is often system-specific, so you should consult your database system's documentation for details. The `LIKE` operator is a more portable and widely supported solution for substring searches.

Why Contains SQL is important

The ability to search for substrings within text data is crucial for many data analysis and retrieval tasks. It allows you to quickly find specific information within large datasets, such as filtering customer records or locating products with particular keywords in their descriptions.

Contains SQL Example Usage


SELECT customer_name
FROM customers
WHERE customer_name LIKE '%Smith%';

Contains SQL Syntax

Common Mistakes

Forgetting to use the wildcard characters (%) or (_).
Using the wrong wildcard for the specific pattern needed.
Misunderstanding the case-sensitivity of `LIKE` (some databases are case-sensitive).
Trying to use `CONTAINS` when it's not supported by the database system.

Frequently Asked Questions (FAQs)

When should I use the SQL `LIKE` operator instead of a `CONTAINS` function?

Use LIKE whenever you need portable, standards-compliant substring searches. LIKE is part of ANSI SQL and works in every major relational database, whereas CONTAINS is proprietary, behaves differently across systems, and may not be enabled by default. Sticking with LIKE ensures your queries run the same way whether you are in Postgres, MySQL, SQL Server, or editing queries inside Galaxy.

How do the `%` and `_` wildcards work in a `LIKE` pattern?

In a LIKE clause, % represents “any sequence of zero or more characters,” while _ matches exactly one character. For example, WHERE name LIKE '%Smith%' returns rows where the substring “Smith” appears anywhere in the name, and WHERE code LIKE 'A_0' matches values such as “AB0” or “A40.” Galaxy’s autocomplete highlights these wildcards so you can see pattern boundaries clearly and reduce typos.

Can Galaxy help me optimize or refactor complex `LIKE` queries?

Yes. Galaxy’s AI copilot is context-aware—it suggests more selective patterns, warns about leading wildcards that can slow down indexes, and can rewrite queries if your schema changes. You can chat with the copilot to convert a vendor-specific CONTAINS expression into a portable LIKE alternative, making your SQL faster and easier to maintain across environments.