How to Select a Substring in Oracle SQL up to a Specific Character?

Crafting with Regular Expressions

Let's raise the bar! You can extract part of a string before a specific character, using REGEXP_SUBSTR:

-- Excuse me, Server. I'll have everything before the underscore. Use REGEXP_SUBSTR, please!
SELECT REGEXP_SUBSTR(your_column, '[^_]+', 1, 1) 
FROM your_table;
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This piece of art delivers the part before the first underscore. If there's no underscore, no worries! It brings you the whole string.

Null Busting Techniques

Sherlock Holmes once said, "When you have eliminated all which is impossible, then whatever remains, however improbable, must handle NULLs." Use NVL with INSTR like this Sherlockian solution:

-- "Elementary, my dear Watson!" If '|' isn't found, deliver the entire string, not NULL.
SELECT NVL(SUBSTR(your_column, 1, INSTR(your_column, '|') - 1), your_column) 
FROM your_table;
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Tips and Tricks for Complex Patterns

Crafting Regular Expressions

Flexibility is a charm! Regular expressions can match complex patterns—the real REGEXP_SUBSTR beauty! Replace 'pattern' with your regex:

-- "One regex to rule them all!" 
SELECT REGEXP_SUBSTR(your_column, 'pattern', 1, 1) 
FROM your_table;
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Chains of SUBSTR and INSTR

Unchain my code! When multiple SUBSTR and INSTR functions start to feel like a chain gang, REGEXP_SUBSTR simplifies your task:

-- "Come on, Just express yourself!" - Said REGEXP_SUBSTR to the chained substrings.
SELECT REGEXP_SUBSTR(your_column, 'your_regex') 
FROM your_table;
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With regular expressions, you can extract parts of a string in varied and unpredictable formats.

A Peek into the Oracle Toolbox

The Mighty INSTR

INSTR isn't just a position finder! It searches from the start or end of a string and can even find nth occurrences. What a multitasker!

Why RTRIM Doesn't Cut it

RTRIM, often mistaken for a string slicer up to a character, is actually a cherry picker. It removes listed characters, not a sequence up to a character.

The NVL Lifesaver

INSTR returning zero because the character's on vacation? Enter NVL. It switches NULL return values with a default valued or the original string, acting like a NULL lifesaver!