There are several ways to find duplicate records and assign a value of ‘Y’ or ‘N’ to them in SQL, depending on the specific database you are using and the structure of your table.
One way to do this in SQL is to use a self-join, where you join a table to itself on the columns that you want to check for duplicates. Then, use a COUNT() function in the SELECT statement to count the number of times each combination of values appears in the table. Finally, use a CASE statement to assign a value of ‘Y’ or ‘N’ to each row based on the count.
Here is an example of how you might do this in SQL:
SELECT t1.*, CASE WHEN count(*) > 1 THEN 'Y' ELSE 'N' END as duplicate FROM your_table t1 JOIN your_table t2 ON t1.column1 = t2.column1 AND t1.column2 = t2.column2 GROUP BY t1.column1, t1.column2
In the above query, the JOIN is done on column1 and column2, you can modify it according to your table structure. The query will find all the rows with duplicate column1 and column2 values and assign a value of ‘Y’ to them. Any rows with unique column1 and column2 values will be assigned a value of ‘N’.
You can also use other method like ROW_NUMBER() OVER (PARTITION BY column1, column2 ORDER BY column1) to assign a unique number to each row and then again use a case statement to find the duplicate records.
It’s also important to note that this query assumes that your table has only one set of duplicate records. If there are multiple sets of duplicates, you can use the DISTINCT keyword in the SELECT statement to eliminate duplicate rows.
Last modified: March 3, 2023