How to calculate the difference between two tables in MySQL?

To calculate the difference between two tables, you can use either NOT IN or LEFT JOIN. Here is a specific example:

1. outside of

SELECT column1, column2
FROM table1
WHERE column1 NOT IN (SELECT column1 FROM table2);

1. Combining tables based on a common key specified in the left table.

SELECT table1.column1, table1.column2
FROM table1
LEFT JOIN table2 ON table1.column1 = table2.column1
WHERE table2.column1 IS NULL;

Both methods can calculate the difference set of the two tables. You can choose the appropriate method based on the specific situation to calculate the difference set.