How Can I Efficiently Update a MySQL Table Based on Matching Values in Another Table?

Updating MySQL Table from Another Based on Value

You want to effortlessly update one MySQL table, 'tobeupdated,' with values from another table, 'original,' based on matching strings stored in a VARCHAR(32) field, 'value.'

Initial Queries and Performance Concerns

Initially, you tried the following query to update 'tobeupdated':

UPDATE tobeupdated, original
SET tobeupdated.id = original.id
WHERE tobeupdated.value = original.value

While successful, this query proved slow and processed only a small fraction of the desired updates.

Optimized Query

To improve performance, consider the following optimized query:

UPDATE tobeupdated
INNER JOIN original ON (tobeupdated.value = original.value)
SET tobeupdated.id = original.id

Understanding the Optimized Query

The 'INNER JOIN' syntax allows for more efficient data retrieval by explicitly specifying the join condition between the two tables. Additionally, indexing the 'tobeupdated.value' and 'original.value' fields significantly accelerates processing.

Simplified Query

For an even simpler solution, you can utilize the 'USING' clause:

UPDATE tobeupdated
INNER JOIN original USING (value)
SET tobeupdated.id = original.id

'USING' simplifies an equi-join by automatically matching columns with the same name across both tables. In this case, both 'tobeupdated' and 'original' have a 'value' column.

Additional Considerations

Ensure adequate index coverage on relevant columns to optimize performance. If the tables are exceptionally large, consider creating a third table for the merged results, although this may not necessarily improve speed.

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