Oracle LIKE & Wildcards 🔍

Mentor's Note: What if you only remember that a student's name starts with "Vi"? You can't use =, but you can use LIKE. It's the search engine of the database world. 💡

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🌟 The Scenario: The Smudged Record 📄

Imagine an old file where the end of the name is unreadable. You only see "Sma...".

• Action: You search for LIKE 'Sma%'.
• Result: You find "Smart", "Small", and "Smathers".

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💻 1. The Wildcard Tools

Wildcard	Meaning	Analogy
%	Zero or more characters	The "Infinite Bridge" 🌉
_	Exactly one character	The "Single Footstep" 👣

Examples

-- Starts with 'A'
SELECT name FROM students WHERE name LIKE 'A%';

-- Has 'sh' anywhere
SELECT name FROM students WHERE name LIKE '%sh%';

-- 4 letter name starting with 'R'
SELECT name FROM students WHERE name LIKE 'R___';

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🏗️ Architect's Note: The Index Trap 🛡️

In Oracle, if you start your pattern with a wildcard (e.g., LIKE '%son'), the database cannot use an index. It must read the whole table.

• Architect's Advice: Always try to put text before the wildcard if performance matters! LIKE 'Son%' is much faster than LIKE '%Son%'.

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📈 Learning Path

• ← Back: BETWEEN Operator
• Next: IS NULL →