Delete Duplicate Rows

The Problem

Using a Self Join

-- keep the row with the smallest id, delete the rest
DELETE e1 FROM employees e1
INNER JOIN employees e2
WHERE e1.id > e2.id
  AND e1.email = e2.email;

How it Works

Summary

• Self-join the table on the duplicate column, delete rows with the larger id.
• This keeps one copy of each unique value.

समस्या

Self Join से

-- सबसे छोटी id वाली row रखें, बाकी delete करें
DELETE e1 FROM employees e1
INNER JOIN employees e2
WHERE e1.id > e2.id
  AND e1.email = e2.email;

कैसे काम करता है

सारांश

• Duplicate column पर table को self-join करें, बड़ी id वाली rows delete करें।
• यह हर unique value की एक copy रखता है।