How Can I Perform Case-Insensitive Searches in Oracle Databases?

Oracle database case-insensitive search method

Oracle Database's default comparison operators (such as LIKE) are case-sensitive. However, case-insensitive searches are possible without using a full-text index.

1. Case conversion method:

Use the UPPER() or LOWER() function to convert all data to the same case:

<code class="language-sql">SELECT * FROM my_table WHERE upper(column_1) = upper('my_string');</code>

or

<code class="language-sql">SELECT * FROM my_table WHERE lower(column_1) = lower('my_string');</code>

Remember to create function-based indexes for case-insensitive searches for greater efficiency.

2. Regular expression method (Oracle 10g and above):

Use the REGEXP_LIKE() function and specify the 'i' match argument to achieve case insensitivity:

<code class="language-sql">SELECT * FROM my_table WHERE regexp_like(column_1, '^my_string$', 'i');</code>

or

<code class="language-sql">SELECT * FROM my_table WHERE regexp_like(column_1, 'my_string', 'i');</code>

It is important to note that regular expressions may interpret special characters differently.

3. Session level modification:

Modify session settings NLS_SORT and NLS_COMP parameters:

<code class="language-sql">ALTER SESSION SET nls_sort=BINARY_CI;
ALTER SESSION SET nls_comp=LINGUISTIC;</code>

This will make all queries in that session case-insensitive. It is recommended to create a language index to improve performance.

Summary:

Which method you choose depends on your specific needs. When using case-insensitive searches, remember to index appropriately to improve performance.

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