Option 2Īssuming the table has been restored with its original data (including duplicate rows), here’s another option for de-duping it. Unless it has been explicitly removed from the table, you can use this as a unique identifier for each row, which enables us to construct the above queries. By default, every row in SQLite has a special column, usually called the rowid, that uniquely identifies that row within the table. ![]() The reason we were able to do this is because of SQLite’s rowid. How To Delete Duplicate Records in SQL Server -Table with Duplicate Records - Temporary Table to store Duplicate Records only RECID INT IDENTITY(1,1). Two of the duplicate rows for “Bark” have also been deleted. To delete the duplicate values, we can modify the above query by replacing SELECT * with DELETE: DELETE FROM PetsĪs expected, one of the duplicate rows for our dog “Wag” has been deleted and the other one remains. This shows us that three rows are going to be deleted when we de-dupe the table in the next step. Option 1īefore we de-dupe the table, we can use the following query to see which row/s will be deleted: SELECT * FROM Pets In any case, below are two options for finding and deleting duplicate rows. If there was a primary key, it would contain unique values across all rows, and there would be no duplicates. Therefore, it’s not a unique identifier for each row, and it cannot be used as a primary key. SQL Query Interview Questions - How to delete duplicates from a table Learn at Knowstar 30.3K subscribers Subscribe 138K views 2 years ago SQL Query Interview Questions This video series. The rows, of course, will not be perfect duplicates because of the existence of the RowID identity field. The PetId column might look like it could be a primary key, but it actually contains duplicate values. I need to remove duplicate rows from a fairly large SQL Server table (i.e. In this case, all columns are duplicates. We can see that the first two rows are duplicates, as are the last three rows. Suppose we have a table with the following data: SELECT * FROM Pets Use the queries in this tutorial to help you find and remove duplicates from an SQL database. Fewer rows also mean queries can execute much faster leading to higher performance. This is often referred to as de-duping the table. However, it lets you free up the space that duplicate rows use. ![]() So if there are three identical rows for example, it deletes two of them and keeps one. These examples delete duplicate rows but keep one. The first method would be to Remove Duplicates in SQL using Group By and Having Clause, & the second method would be SQL Delete Duplicate Rows in SQL Server. ![]() The following options can be used to delete duplicate rows in SQLite.
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |