T sql delete duplicate rows

I have a table with a very large amount of rows. Duplicates are not allowed but due to a problem with how the rows were created I know there are some duplicates in this table. I need to eliminate the extra rows from the perspective of the key columns. How to delete duplicate rows in SQL. The aforementioned script will create the table, People, with records, where records are duplicates (if we consider similar Name field) or records are duplicates (if we consider all of Name, City, State fields).

The rowcount value should be n-the number of duplicates for a given key value. In this example, there are duplicates so rowcount is set to 1. If the GROUP BY query returns multiple rows , the set rowcount query will have to be run once for each of these rows. Each time it is run, set rowcount to n-the number of duplicates of the particular PK value.

Use DELETE statement to remove the duplicate rows. Let’s set up a sample table for the demonstration. People with application development background would consider using a cursor to try to eliminate duplicates.

The basic idea is to order the contents of the table, iterate through the ordered rows , and check if the current row is equal to the previous row. If it does, then delete the row. An explanation of how to find rows with duplicate values in a table using SQL. Finishes by showing how to stop people entering new duplicates ! In above query, the function row _number generates a row number in each row for the same empiname group of result set. See screenshot of CTE table CTE_ Duplicates.

The query delete from CTE_ Duplicates where rownumber! Sometimes we required to delete duplicate rows from a table although the table has a UniqueID Column with identity. Group by with having into a cursor. Then, the DELETE statement deletes all the duplicate rows but keeps only one occurrence of each duplicate group. If you have got a situation that you have multiple duplicate records in a table, so at the time of fetching records from the table you should be more careful.

You make sure that you are fetching unique records instead of fetching duplicate records. To overcome with this problem we use DISTINCT keyword. To find duplicates rows in a table you need to use a Select statement that contains group by with having keyword.

Another option is to use the ranking function Row _Number(). Understanding CTE query is bit difficult so if you still don' t understand how CTE is working, no worries see Methodsame job but different approach. The following shows the steps for removing duplicate rows using an intermediate table: Create a new table with the structure the same as the original table that you want to delete duplicate rows. Insert distinct rows from the original table to the immediate table. There are tons of duplicate cities in this table.

SQL DELETE DUPLICATE ROWS. I ran this query and it shows me the number of occurrences of each city. I want to delete all the duplicates except for 1.