How to remove duplicates in Netezza?

@lyda.dickens In Netezza, you can use the DISTINCT keyword to remove duplicate rows from the result set of a SELECT statement. For example:

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SELECT DISTINCT column1, column2, ...
FROM table_name;

This will return all the unique rows in the table, with no duplicates.

If you want to keep only the first row of each set of duplicates, you can use the row_number() function to assign a unique row number to each row, and then use a subquery to select only the rows with a row number of 1:

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SELECT *
FROM (
    SELECT *, row_number() OVER (PARTITION BY column1, column2, ... ORDER BY column1) AS rn
    FROM table_name
) t
WHERE t.rn = 1;

This will return one row for each set of duplicates, with the first row of each set being returned.

You can also use the EXCEPT operator to remove duplicates from the result set. The EXCEPT operator returns all rows from the first SELECT statement that are not returned by the second SELECT statement. For example:

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SELECT column1, column2, ...
FROM table_name
EXCEPT
SELECT column1, column2, ...
FROM table_name;

This will return all the unique rows in the table, with no duplicates.

@lyda.dickens 

Another way to remove duplicates in Netezza is to use the GROUP BY clause. The GROUP BY clause groups the result set by one or more columns and allows you to perform aggregate functions such as COUNT, SUM, AVG, etc. By grouping the result set, you can eliminate duplicate rows.

Here is an example:

SELECT column1, column2, ... FROM table_name GROUP BY column1, column2, ...;

This query will return the unique combinations of column1, column2, ... from the table and eliminate any duplicates.

Additionally, you can use the ROW_NUMBER() function to remove duplicates while keeping only one row for each duplicate set. The ROW_NUMBER() function assigns a unique number to each row in the result set based on the specified ordering.

Here is an example:

SELECT * FROM ( SELECT column1, column2, ..., ROW_NUMBER() OVER (PARTITION BY column1, column2, ... ORDER BY column1) AS row_num FROM table_name ) t WHERE row_num = 1;

This query will assign a row number to each row within each duplicate set based on the ordering specified in the ORDER BY clause. Then, it will select only the rows with a row_num value of 1, effectively removing duplicates while keeping the first row from each set of duplicates.