Cursors are not the best solution when talking about performance but,

If you run into issues with another coding technique and need to get something done quickly, using a cursor may be a viable alternative. It may take longer to process the data, but the coding time might be much less. If you have a one-time process or nightly processing, this could do the trick.

This article contains a good description, example and alternatives to cursors.

https://www.mssqltips.com/sqlservertip/1599/sql-server-cursor-example/

We need to do this all the time. This is just one example of a way to load multiple Excel data files into a table.

http://www.sqlservercentral.com/articles/OPENROWSET/163645/

The same concept could be used to load flat files.

Scalar Functions are very useful in SQL Server but they need to be used correctly. You can find a simple query takes much too long to run and the only problem is that the function needs to calculate on every row returned. There are many ways to write queries and this article will show you why scalar functions can cause you headaches.

http://www.sqlservercentral.com/articles/T-SQL/135321/?utm_source=SSC&utm_medium=pubemail

The OUTPUT clause in T-SQL allows you to see what was actually inserted or deleted. This can be used for auditing or archiving purposes.

OUTPUT Clause Basics

http://www.sqlservercentral.com/articles/T-SQL/155154/?utm_source=SSC&utm_medium=pubemail

Getting more done with OUTPUT

http://www.sqlservercentral.com/articles/output/147336/

While DISTINCT and GROUP BY are identical in a lot of scenarios, here is one case where the GROUP BY approach definitely leads to better performance.

The DISTINCT variation took 4X as long, used 4X the CPU, and almost 6X the reads when compared to the GROUP BY variation.

https://sqlperformance.com/2017/01/t-sql-queries/surprises-assumptions-group-by-distinct

By joining two data-sets together by their common keys, we cause the EXCEPT statement to compare the remaining columns.  This approach to check row differences can reduce errors by removing the tedious hand-coding of column-by-column comparisons as well as required null-handling logic.

http://www.sqlservercentral.com/articles/EXCEPT/107520/?utm_source=SSC&utm_medium=pubemail

The use of wildcard character searches in SQL Server scripts is common for all of us. This article makes some good points on how to do it correctly and what to avoid.

Please read this article. It may help you better understand your options when it comes to string searches.

http://www.sqlservercentral.com/articles/T-SQL/130558/?utm_source=SSC&utm_medium=pubemail