Oracle DB: How can I write query ignoring case?

Query customization for case-insensitive search

"LIKE" operator for pattern matching

For pattern matching, pair the LIKE operator with UPPER or LOWER functions:

SELECT * FROM table_name WHERE UPPER(column_name) LIKE UPPER('%search_pattern%');
 -- The % symbol is like a party, everyone (characters) gets in!
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This approach ensures a case-insensitive wildcard search.

Session settings for case-insensitive comparison

You can modify the session to default to a case-insensitive comparison using the ALTER SESSION command:

ALTER SESSION SET NLS_COMP = 'LINGUISTIC';
ALTER SESSION SET NLS_SORT = 'BINARY_CI';
-- Changing the session settings, like changing the mood lighting for your queries!
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Expanding capability with REGEXP_LIKE

To employ the versatility of regular expressions, use REGEXP_LIKE with the 'i' option for case-insensitivity:

SELECT * FROM table_name WHERE REGEXP_LIKE(column_name, 'search_pattern', 'i');
-- Don't you just love options! 'i' for case-insensitive, 'i' for incredible.
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Optimizing performance with function-based indexes

Function-based indexes can help maintain performance when conducting frequent case-insensitive searches:

CREATE INDEX idx_upper_column_name ON table_name (UPPER(column_name));
-- This function-based index is like giving your queries a speed boost!
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Advanced Oracle techniques for case-insensitive queries

Intense searches with Oracle Text

For intricate searches, the Oracle Text CONTAINS SQL function enables case-insensitive search:

SELECT * FROM table_name WHERE CONTAINS(column_name, 'search_string', 1) > 0;
-- This ain't your average search! Oracle Text, for when you need to go deeper.
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Understanding potential bottlenecks

• Overusing UPPER and LOWER functions without proper indexing can lead to full table scans.
• Different functions in the query and index could result in bypassing the index.
• REGEXP_LIKE searches can be less efficient than basic string comparisons, so apply them judiciously.

Following the best practices

• Utilize function-based indexes to boost performance on large data sets.
• Implement session-level changes for consistent case-insensitivity across various queries.
• Ensure NLS settings are identical across various environments (development, testing, production).