Mysql combine two columns and add into a new column

Add combined columns to the table

You can preserve the combined data directly within your table. Use the ALTER TABLE command to append a new column, and store the fusion of pre-existing columns into it.

ALTER TABLE your_table
ADD combined_column VARCHAR(50); -- Think about the length. Make Goldilocks proud. Not too long, not too short, just right!

UPDATE your_table
SET combined_column = CONCAT(column1, ' - ', column2); -- We're fusing them together. It's like an Avengers assemble moment!
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Safeguarding data accuracy

In the world of relational databases like MySQL, data integrity is sacred. You must ensure that combining data into a new column doesn't compromise the data structure or induce data loss.

UPDATE your_table
SET combined_column = CONCAT(column1, ' - ', column2) -- We're combining, not creating chaos!
WHERE combined_column IS NULL or combined_column != CONCAT(column1, ' - ', column2); -- Only when it's emptier than my fridge late at night or out of sync
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Keep it fresh with triggers

Triggers in MySQL are like a self-driving car—they auto-update! By setting BEFORE INSERT and BEFORE UPDATE triggers, you ensure your combined_column remains up-to-date regardless of data changes:

DELIMITER //

-- Trigger - the database's little elf working in stealth mode
CREATE TRIGGER before_insert_your_table
BEFORE INSERT ON your_table FOR EACH ROW
BEGIN
    SET NEW.combined_column = CONCAT(NEW.column1, ' - ', NEW.column2);
END; -- It's like that song ending note: the last touch

CREATE TRIGGER before_update_your_table
BEFORE UPDATE ON your_table FOR EACH ROW
BEGIN
    SET NEW.combined_column = CONCAT(NEW.column1, ' - ', NEW.column2);
END; -- And scene!

DELIMITER ;
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Live data combination—ditch permanent updates

Some stars shine brighter in the moment. If you'd rather keep your table alterations minimal, consider combining data in real time. Use CONCAT in a SELECT statement to avoid modifying the table:

SELECT CONCAT(column1, ' - ', column2) AS combined_display
FROM your_table; -- Voila! They're combined. No surgery needed!
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Pair the old and the new

Backfilling the combined column for existing records ensures data consistency. It's like giving everyone at a party the same amount of cake:

-- Everyone gets a slice!
UPDATE your_table
SET combined_column = CONCAT(column1, ' ', column2)
WHERE combined_column IS NULL; -- Again, for the hungry ones
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Think before merging

Data duplication won't win popularity contests—it increases the database size and might add unnecessary burdens. Evaluate if this merge is required at the database level or could be achieved at the application layer.