How to delete duplicates with CTE?

How to delete duplicates with CTE?

1. Open SQL Server 2014 or your choice. Create table with name Employees.
2. Insert some duplicate record. Below is sample record.
3. Write CTE (Common table expression) and partition records. WITH EmployeesCTE as.
4. Write query for delete duplicate record with CTE (common table expression). WITH EmployeesCTE as.

Can you delete from CTE?

It’s definitely possible to delete from a CTE, sql server infers the underlying table from the select statement.

Does deleting from CTE delete from table?

We run a delete against a CTE in SQL Server and the table’s values are affected – this differs from taking data from a table to a temp table and removing data from the temp table. The source table still has the records. Even with one table’s data in the delete statements, this will not remove data.

Is CTE better than temp table?

Looking at the SQL Profiler results from these queries (each were run 10 times and averages are below) we can see that the CTE just slightly outperforms both the temporary table and table variable queries when it comes to overall duration.

Does inner join remove duplicates?

Now if I join the table on recid, it will give 0 result, there will be no duplicates because recid is unique. But if I join on firstname and lastname column, which are not unique and there are duplicates, I get duplicates on inner join. The more columns I add on join, the worse it becomes (more duplicates are created).

Can we use temp table inside CTE?

You cannot create and drop the #TEMP table within the CTE query.

How to remove duplicates from a table using CTE?

The following query uses a CTE to remove duplicate records. Keeping the latest of the duplicates based on their insertion Id. To accomplish this, a PARTITION is used to group duplicates together and they are ordered most recent to oldest. Using ROW_NUMBER we number the duplicates and delete anything that has a row number greater than 1.

How to delete duplicate records from a table?

Recursive Query is the Common Table Expression (CTE) query which refers to the same CTE by recursion, and this is the main part of recursive CTE. 1) Create temporary with some dummy records. 2) Insert duplicate records in the created temporary table.

How is a CTE similar to a derived table?

Similar to a derived table in that it is not stored as an object and lasts only for the duration of the query. Unlike a derived table, a CTE can be self-referencing and can be referenced multiple times in the same query. The following query uses a CTE to remove duplicate records. Keeping the latest of the duplicates based on their insertion Id.

Can a CTE be referenced multiple times in the same query?

Unlike a derived table, a CTE can be self-referencing and can be referenced multiple times in the same query. The following query uses a CTE to remove duplicate records. Keeping the latest of the duplicates based on their insertion Id.