Wednesday, May 4, 2016 Liverpool Exhibition Centre One day session* *£349 until April 9, 2016. £399 thereafter – This training day has sold out!
I will be presenting this session in a Training Day at the SQLBits conference in Liverpool, UK. Reserve your seat for this one day session here.
I’ve known for a long time now that teaching makes me a better database administrator and performance tuner. But I’ve had a hard time figuring out why.
Joins can be tricky. And where you put your ‘where’ clause may mean more than you think!
Take these two queries from the AdventureWorksDW sample database. The queries are both looking for data where SalesTerritoryCountry = ‘NA’ and they have the same joins, but the first query has a predicate on SalesTerritoryCountry while the second has a predicate on SalesTerritoryKey.
/* Query 1: Predicate on SalesTerritoryCountry */ select ProductKey, OrderDateKey, DueDateKey, ShipDateKey, CustomerKey, PromotionKey, CurrencyKey, fis.SalesTerritoryKey, SalesOrderNumber, SalesOrderLineNumber, RevisionNumber, OrderQuantity, UnitPrice, ExtendedAmount, UnitPriceDiscountPct, DiscountAmount, ProductStandardCost, TotalProductCost, SalesAmount, TaxAmt, Freight, CarrierTrackingNumber, CustomerPONumber, OrderDate, DueDate, ShipDate from dbo.FactInternetSales fis join dbo.DimSalesTerritory st on fis.SalesTerritoryKey=st.SalesTerritoryKey where st.SalesTerritoryCountry = N’NA’ GO
Execution plans got a cool new piece of diagnostic information in SQL Server 2012 SP3, SQL Server 2014 SP2, and SQL Server 2016: “Number of Rows Read”. In fancy language, this is “better diagnostics” when a query plan has “residual predicate pushdown” (KB 3107397).
Recompile hints have been tough to love in SQL Server for a long time. Sometimes it’s very tempting to use these hints to tell the optimizer to generate a fresh execution plan for a query, but there can be downsides.
Working with table partitioning can be puzzling. Table partitioning isn’t always a slam dunk for performance: heavy testing is needed. But even getting started with the testing can be a bit tricky!
Here’s a (relatively) simple example that walks you through setting up a partitioned table, running a query, and checking if it was able to get partition elimination.
One perk to filtered indexes that may not be obvious at first is that you get an extra “dimension”– almost an extra kind of key column. This can be useful for some queries that can be tricky to index.
Copyright (c) 2025, Catalyze SQL, LLC; all rights reserved. Opinions expressed on this site are solely those of Kendra Little of Catalyze SQL, LLC. Content policy: Short excerpts of blog posts (3 sentences) may be republished, but longer excerpts and artwork cannot be shared without explicit permission.