Question

How to eliminate duplicate rows in sql without using distinct

Answer 1

To eliminate duplicate rows in SQL without DISTINCT, use a GROUP BY clause or window functions like ROW_NUMBER(). GROUP BY all columns or partition by these columns using ROW_NUMBER() and filter where the row number is 1.

Step-by-step explanation:

To eliminate duplicate rows in SQL without using DISTINCT, you can use a GROUP BY clause or a window function if supported by your SQL database system. One of the common approaches is to group by all columns of the table.

Here's an example using GROUP BY:

1. Select all columns you want to display in the result.
2. Add the GROUP BY clause, grouping by all the selected columns.

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

If your SQL version supports window functions, you can use ROW_NUMBER() to eliminate duplicates.

1. Use the ROW_NUMBER() function partitioned by the columns that could have duplicates.
2. Select rows where the row number is 1, indicating the first occurrence of the row, thus eliminating duplicates.

SELECT * FROM (
SELECT *, ROW_NUMBER() OVER(PARTITION BY column1, column2, ...) AS rn
FROM your_table
) AS subquery
WHERE subquery.rn = 1;

Be mindful that the GROUP BY method will not work if there are rows with non-duplicate values for all columns, whereas the window function works by considering the order and partitioning of rows, effectively handling such scenarios.