What is a correlated sub-query?

What is a correlated sub-query? A correlated sub-query is a special type of query containing a sub-query. The sub-query contained in the query actually requests values from
the outside query, creating a situation similar to a loop.

Correlated subquery in sql Part 60

SELECT NAME,

(SELECT SUM(QUANTITYSOLD) FROM tblProductSales Where ProductID=tblProducts.Id) as QtySold FROM tblProducts

What to choose for performance SubQuery or Joins Part 62

To drop query cache:


CHECKPOINT;
GO
DBCC DROPCLEANBUFFERS; – -clears query cache
GO
DBCC FREEPROCACHE; – clears execution plan cache
GO