How to improve aggregations after joins in Power Query?
If one of your tables has a primary key, the method Chris Webb describes here works just as good: Chris Webb’s article on how to improve performance on aggregations after joins using primary keys . You can follow along the different methods in this file: PerformanceAggregationsAfterMerges1_Upload.zip
How to improve the performance of SQL query?
To improve performance you either need to reduce the result set or perform a nasty trick (eg make a denormalized copy of the data). From your query plan I can conclude that the tables referred to as s, n and q do not have an index on the field they are being joined on.
What happens when Power Query is joined to another table?
When you join a table to another table in Power Query, the UI gives you the option to either expand the columns (default) or aggregate the contents of the joint tables. That’s useful if multiple rows are returned for the rows of the table that has been joined to (left table):
Which is better join method or window function?
It seems that the join method has more logical reads than the window function method, while the execution time for the former is actually less. Is it because the former has a better parallelism? I like the window function method because of the concise code, is there any way to speed it up for this specific problem?
How can I improve the performance of my SQL query?
Yes, you can improve query performance simply by replacing your SELECT * with actual column names. Do not use * in your SQL queries, instead, use actual column names that you want to return . The database may scan column names and replace * with actual columns of the table.
Why does the join clause slow down SQL?
UNION clause causes sorting data in the table and that slows down SQL execution. Instead, use UNION ALL and remove duplicates by adding more columns before applying UNION all. Almost all databases support joining tables using JOIN clause and WHERE clause.
Why do you select two columns in a SQL query?
There are many reasons for that recommendation, like: SELECT * Retrieves unnecessary data besides that it may increase the network traffic used for your queries. When you SELECT *, it is possible to retrieve two columns of the same name from two different tables (when using JOINS for example).