Peter Lalovsky

Keep it simple

Optimization

T-SQL: Avoid MERGE. Write separate statements instead

2021-11-04 in Optimization / T-SQL tagged MERGE / Optimization / T-SQL by Peter Lalovsky

The MERGE statement was introduced in SQL Server 2008 and the developers embraced it immediately. Later a feedback came and the statement was criticized as not very efficient. Aaron Bertrand collected some links about this here. MERGE statement anatomy The MERGE statement joins ‘source’ and ‘target’ tables and runs INSERT, […]

T-SQL: Avoid Cursor. Use WHILE instead

2021-11-03 in Optimization / T-SQL tagged CURSOR / Optimization / T-SQL / WHILE by Peter Lalovsky

Set-based Database Development As database developer, we need to switch our mindsets to “Set-based thinking”. In simple words we need to manipulate the data as a “set”. An example of set-based database development is: JOIN tables Aggregate the result Calculate the portion (%) of a row to the total of […]

T-SQL Optimization: Nonclustered Index and GROUP BY

2015-01-06 in Optimization / T-SQL tagged Optimization / Performance / The Price I Pay by Peter Lalovsky

In this example I play with the performance of a query that groups the data.