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Tuesday, 10 May 2016

Query to Finding and Deleting Duplicate Rows

The following statement will find and display all duplicate rows in a table, except the row with the maximum rowid:

SELECT *
FROM <tableA> a
WHERE rowid  <>  (SELECT max(rowid)
FROM <tableB> b
WHERE a.<column1> = b.<column1>
AND a.<column2> = b.<column2> -- make sure all columns are compared
AND a.<column3> = b.<column3>;

Note:  Duplicate rows which contain only NULL values will not be identified by above statement.
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