How to Perform an Exact Search with Underscores in Oracle SQL Using CONTAINS

Learn how to perform an exact search with underscores in Oracle SQL using the CONTAINS function. This guide details the steps to achieve precise searches in Oracle databases.
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In Oracle SQL, performing an exact search can sometimes be tricky, especially when dealing with special characters like underscores. Normally, the underscore (_) character in SQL is a wildcard for a single character. This can complicate things when you need to find string literals that include underscores. However, Oracle SQL provides a way to handle this scenario using the CONTAINS function.

Understanding the Problem: Underscores in SQL
In SQL, the underscore is a wildcard that represents any single character. For example, the query SELECT * FROM my_table WHERE column_name LIKE 'A_B'; will match any strings where 'A' and 'B' are separated by exactly one character. But, what if you actually want to find the string A_B? This is where the CONTAINS function becomes extremely useful.

Using the CONTAINS Function for Exact Searches
The CONTAINS function is part of Oracle's Text feature, which allows for enhanced query capabilities such as full-text and context searches.

To use the CONTAINS function for an exact search with underscores:

Create a Text Index:
You need to create a text index on the column where you want to perform the search. This is required for the CONTAINS function to work.

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Perform the Exact Search:
Use the CONTAINS function to search for the exact string including underscores.

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In this example, 'A_B' is treated as a string literal, and the CONTAINS function will search for this exact sequence of characters in the specified column.

Sample Use Case
Consider a table employee_records with a column employee_code that may include underscores. To find all records where the employee_code is exactly A_B, you would first create the necessary text index:

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Then, perform the search:

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Conclusion
Using the CONTAINS function in Oracle SQL is a practical approach to conducting exact searches involving underscores. By creating a text index and leveraging the CONTAINS function, you can precisely locate string literals that include special characters.

Mastering this technique can greatly enhance your ability to perform accurate and effective searches in Oracle databases.