How does a SQL query work? How does it get compiled? Is the from clause compiled first to see if the table exists? How does it actually retrieve data from the database? How and in what …

Apr 14, 2011 · All standards-compliant SQL dialects work the same way. Note: To compare if your value is not null, you use IS NOT NULL, while to compare with not null value, you use <> …

The database engine does not have to run the subquery entirely. If a single record is matched, the EXISTS operator returns true, and the associated other query row is selected. The inner …

Nov 27, 2013 · Does the SqlBulkCopy create a data file? I would like to understand this stuff to work out whether I can use the bulk insert functionality in SQL. If I write a SQL statement that …

Given that indexing is so important as your data set increases in size, can someone explain how indexing works at a database-agnostic level? For information on queries to index a field, check …

May 30, 2017 · GROUP BY returns a single row for each unique combination of the GROUP BY fields. So in your example, every distinct combination of (a1, a2) occurring in rows of Tab1 …

But, you would be wrong. The way parameterized queries work, is that the SQL query is sent as a query, and the database knows exactly what this query will do, and only then will it insert the …

Aug 6, 2018 · The SQL COALESCE() function can be described in a single sentence: COALESCE returns the first non-NULL value passed for each row. Please rephrase this …

I have 4000 rows for example, and I define X limit. The query stops after it finds X rows? or the query finds all the rows and then takes X rows from the found rows? Thank you.

Jul 21, 2015 · SELECT TOP (2) * FROM MstConfigSettings ORDER BY DefaultItemId The execution plan shows and So, when I don't apply ORDER BY the steps are different (there is …