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How could I filter out the duplicate value in a column with SQL syntax?
Thanks.
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To select duplicate values, you need to create groups of rows with the same values and then select the groups with counts greater than one. You can achieve that by using GROUP BY and a HAVING clause.
One way to find duplicate records from the table is the GROUP BY statement. The GROUP BY statement in SQL is used to arrange identical data into groups with the help of some functions. i.e if a particular column has the same values in different rows then it will arrange these rows in a group.
The go to solution for removing duplicate rows from your result sets is to include the distinct keyword in your select statement. It tells the query engine to remove duplicates to produce a result set in which every row is unique.
A common question, though filtering out suggests you want to ignore the duplicate ones? If so, listing unique values:
SELECT col FROM table GROUP BY col HAVING (COUNT(col) =1 ) If you just want to filter so you are left with the duplicates
SELECT col, COUNT(col) AS dup_count FROM table GROUP BY col HAVING (COUNT(col) > 1) Used www.mximize.com/how-to-find-duplicate-values-in-a-table- as a base in 2009; website content has now gone (2014).
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