Kalen Delaney

Kalen Delaney has been working with SQL Server for over 30 years, and is one of the world's most respected authorities on SQL Server and a much sought after trainer and speaker. Her book on "SQL Server Internals" is consistently cited as a must-read for aspiring SQL Server professionals.

In-Memory OLTP eBook Download

SQL Server Internals: In-Memory OLTP

In this book, Kalen Delaney explains how the 2016 In-Memory OLTP engine works, how it stores and manipulates data, and how, even with all data stored in memory and no locking or latching, it can still guarantee the ACID properties of all transactions.

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2023-04-28 (first published: )

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SQLServerCentral Article

SQL Server Concurrency: Locking, Blocking and Row Versioning

Your application can have impeachable indexes and queries, but they won't help you if you can't get to your data because another application has it locked. That's why every DBA and developer must understand SQL Server concurrency and how to troubleshoot excessive blocking or deadlocking. Kalen Delaney's book is your guide.

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2013-08-26

5,185 reads

SQL Server Concurrency eBook cover

SQL Server Concurrency: Locking, Blocking and Row Versioning

Your application can have impeachable indexes and queries, but they won't help you if you can't get to your data because another application has it locked. That's why every DBA and developer must understand SQL Server concurrency and how to troubleshoot excessive blocking or deadlocking. Kalen Delaney's book is your guide.

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2012-10-02

3,673 reads

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Fun with JSON II

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Changing Data Types

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Question of the Day

Fun with JSON II

I have some data in a table:

CREATE TABLE #test_data
(
    id INT PRIMARY KEY,
    name VARCHAR(100),
    birth_date DATE
);

-- Step 2: Insert rows  
INSERT INTO #test_data
VALUES
(1, 'Olivia', '2025-01-05'),
(2, 'Emma', '2025-03-02'),
(3, 'Liam', '2025-11-15'),
(4, 'Noah', '2025-12-22');
If I run this query, how many rows are returned?
SELECT t1.[key] AS row,
       t2.*
FROM OPENJSON(
     (
         SELECT t.* FROM #test_data AS t FOR JSON PATH
     )
             ) t1
    CROSS APPLY OPENJSON(t1.value) t2;

See possible answers