Can SQL Server piece together two different indexes in a single-table query, rather than just giving up and scanning a suboptimal clustered index? The short answer is: yes, in a fairly narrow band of conditions.
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Scan hundreds of SQL Saturday raffle tickets. Fast.
If you’re an organizer, sponsor and/or an exhibitor at a SQL Saturday event, you often collect raffle tickets from attendees. In exchange for giving you their contact information, they have the opportunity to win cool raffle prizes.
Here’s the thing, though. Raffle tickets can be a bit painful to scan on your mobile phone. You point the phone at the QR code, then click the URL that opens up the browser, after which the SQL Saturday web service takes another second or two (or three) to load. This is fine when you have just a few tickets, but it can be mindnumbing if you have hundreds.
What can I say, I’m lazy.
Continue readingReading a query plan
Knowing how to read a query plan is absolutely key to optimizing SQL Server query performance. The query plan tells you how SQL Server goes about running your query, including what indexes are used (and how), what join strategies are applied and a lot of other information. If you can read the query plan, you can make the appropriate changes to indexes, query hints, join conditions, etc to tune your workload for optimum performance.
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