How can I append a string to an existing field in MySQL?

Cracking the CONCAT() nut

The CONCAT() function is like a superglue for strings. It allows you to append, or should I say stick additional data onto your existing values. Very handy for dynamic updates.

Important! Safety first

• Backup, backup, and did I mention backup your data before any update operations.

• With transactions, you can always perform a ROLLBACK; magic trick if errors pop up:

  /* If you need an escape hatch | */
  BEGIN;
  UPDATE your_table SET your_column = CONCAT(your_column, 'string_to_append') WHERE your_condition;
  ROLLBACK; /* Harry Potter loves this spell | Or COMMIT; if you're brave enough */
  

• Put it to test with a sample data before moving on to the real deal.

• Null values can be tricky devils, handle them wisely to avoid unintentional data loss:

  /* null? What null? | */
  UPDATE your_table SET your_column = CONCAT(IFNULL(your_column,''), 'string_to_append') WHERE your_condition;
  

When CONCAT() feels like an art

• Articulate conditionally. Use CASE statements within CONCAT to decide what to append :

  /*
  I feel like a poet, appending strings conditionally |
  */
  UPDATE your_table 
  SET your_column = CONCAT(your_column, 
                           CASE WHEN your_condition THEN '_suffix' ELSE '' END)
  WHERE another_condition;
  

• Optimizing? Yes please. Run updates in batches for dealing with large datasets.

• Keep a close eye on what's changing. Maintain a change log for tracking down who's messing with the data.

Special Cases: Handling with care

Null isn't always null

In SQL "null" doesn't mean absence, it represents an unknown. Handle these unknowns to prevent any relational head-scratching:

/* Null puts a '?' in your code, add default value until you find an answer |*/
UPDATE your_table SET your_column = CONCAT(COALESCE(your_column, ''), 'string_to_append') WHERE your_condition;


Update spree

Need to append strings to multiple columns at once? Here's how to do it:

/* Multitasking level: SQL */
UPDATE your_table
SET column1 = CONCAT(column1, '_end'),
    column2 = CONCAT(column2, '_end')
WHERE your_condition;


Maybe you like your data extra large. No problem, just adjust the field size before the update.