Sql query to make all data in a column UPPER CASE?

Step-by-step guide: Case conversion in SQL

Know your database: Case sensitivity

Before you dive in, it's good to know that SQL databases aren't created equal. Some are case-insensitive by default (looking at you, MySQL). Others, with PostgreSQL leading the pack, are case-sensitive.

Friendly reminder: Check your data type

Remember, the UPPER() function only works with text data types. Applying it to non-text data types might give you an uninvited error party.

Temporary case change: UPPER() in SELECT

If you just want to show off your data in all upper case to impress your boss but don't want to modify the actual data - use SELECT:

-- Turn your eardrums on, the data is about to shout!
SELECT UPPER(columnName) AS LoudData FROM tableName;
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The finer points: Advancing your UPPER() game

Case sensitive search: COLLATE

The COLLATE keyword is like your fine-tuning knob for comparison sensitivity. Let's say you want exactly "SOME DATA", not "SomE dAtA". Here's how:

-- No more soft whispers. If you're not yelling "SOME DATA", I'm not listening!
SELECT * FROM tableName WHERE columnName COLLATE SQL_Latin1_General_CP1_CS_AS = 'SOME DATA';
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In SQL Server, this example does a case-sensitive comparison.

Cover your bases: Testing before updating

Just like strapping on a parachute before jumping out of a plane, always preview your changes with a SELECT before an UPDATE. Safety first!

-- Let's see how loud you can be...
SELECT columnName, UPPER(columnName) AS previewColumn FROM tableName;
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Play nice: Avoiding table locks

Updating a large table can be like the office lunch rush, creating bottlenecks and grumpy coworkers. Consider updating in batches to keep the peace.

Pro tips for efficient UPPER()

Hold on! What about my indexes?

Transforming a column with UPPER() can twist your index performance. If your data frequently uses that column, consider creating a new upper case index.

Special characters: Friend or foe?

Remember, some characters don't play nice with UPPER(). For example, accented characters or specific languages. Be sure to test your conversion with different scenarios to ensure consistent results.

Database nuances: Know your terrain

Every SQL database system has its own way. MySQL's UPPER() nicely handles Unicode. In contrast, PostgreSQL might require an unaccent module sidekick.