Updating Data In Common Table Expressions

Kenneth Fisher shows that you can directly update a table referenced in a common table expression:

CTEs are cool things. You can essentially create one or more in-line view(s) within your query. One thing that isn’t overly well known is that you can actually update the data within the CTE. No, I don’t mean using using the UPDATE statement with a CTE but actually running the update through the CTE.

This is really powerful when combined with window functions, like only updating the first record given a particular partition.  You can also delete, which makes duplicate detection and deletion fairly straightforward.

Related Posts

Converting Binary To Hex With T-SQL

Dave Mason uses STRING_SPLIT to convert binary values to their hex equivalents: I started pondering it for a bit and began to wonder if I could use the new for SQL Server 2016 STRING_SPLIT function to convert a binary string to decimal. The thought process was to split the string into rows of CHAR(1) values, along with an in-string character […]

Read More

Faster Scalar Functions In SQL Server 2019

Brent Ozar looks at improvements the SQL Server team has made to scalar functions in 2019: My database has to be in 2019 compat mode to enable Froid, the function-inlining magic. Run the same query again, and the metrics are wildly different: Runtime: 4 seconds CPU time: 4 seconds Logical reads: 3,247,991 (which still sounds bad, […]

Read More

Categories

October 2017
MTWTFSS
« Sep Nov »
 1
2345678
9101112131415
16171819202122
23242526272829
3031