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16 CPU

SQL SERVER – 16 CPU vs 1 CPU : Performance Comparison – SQL in Sixty Seconds #142

November 10, 2020
Pinal Dave
SQL Video
Execution Plan, SQL CPU, SQL in Sixty Seconds, SQL Scripts, SQL Server

Well, let us figure out the answer to this question in today’s blog post where I will be doing a performance comparison of 16 CPU vs 1 CPU.

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A continuous thread passes through an external fixture and returns to its loom.

SQL SERVER – PREEMPTIVE Waits and Scheduler Context

November 9, 2020
Pinal Dave
SQL Performance
SQL Scripts, SQL Server, SQL Wait Stats

Preemptive waits can measure work outside SQL Server cooperative scheduling. A customer asked about their increase during a health check.

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Gouache painting of a trail post with three arrow pointers, one of them vermilion

Multiple OPTIMIZE FOR Hints in One Query: Value or UNKNOWN

November 6, 2020
Pinal Dave
SQL Performance
Execution Plan, Parameter Sniffing, Query Hint, SQL Scripts

Multiple OPTIMIZE FOR hints in one query are written as one list: each parameter gets its own value or UNKNOWN. This post compiles the same query six ways, reads the compile values and estimated rows from the plan cache, and shows which combinations SQL Server accepts.

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SQL SERVER – DISTINCT Does Not Guarantee ORDER BY

November 5, 2020
Pinal Dave
SQL Tips and Tricks
Execution Plan, SQL Operator, SQL Order By, SQL Scripts, SQL Server

DISTINCT removes duplicate result rows without guaranteeing their order. My original claim that it always sorts output was incorrect.

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TOP and DISTINCT

SQL SERVER – TOP and DISTINCT – Epic Confusion – SQL in Sixty Seconds #141

November 4, 2020
Pinal Dave
SQL Video
SQL in Sixty Seconds, SQL Operator, SQL Performance, SQL Scripts, SQL Server

DBAs from the client’s organization ended up an argument about how T-SQL works. The discussion was about the epic confusion about TOP and DISTINCT.

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Gouache painting of a seedling in a clay pot beside a glass bell jar covering a lit candle

DDL in a Transaction: What Rolls Back and What Blocks

November 3, 2020
Pinal Dave
SQL Tips and Tricks
SQL Scripts, SQL Transactions, Transaction Isolation

DDL in a transaction works in SQL Server: CREATE, ALTER and DROP roll back like any other change. This post proves it with a small demo, lists the statements that are refused inside a transaction, and shows which locks an open DDL transaction holds and who has to wait for them.

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Gouache painting: a long wooden shelf of identical round teapots, each with a plain linen string tied around its handle so they can be told apart, the first teapot left bare and one string dyed vermilion

Uniquifier: The Hidden Cost of Duplicate Clustered Keys

November 2, 2020
Pinal Dave
SQL Performance
Clustered Index, SQL Data Storage, SQL DMV, SQL Index

The uniquifier is a hidden 4-byte value that SQL Server adds to duplicate keys in a non-unique clustered index. This post measures its real cost row by row on SQL Server 2025 and shows it on the page. It also compares it with a unique key you choose yourself.

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