Gouache painting of two seed trays, one with seeds planted in order ending in a vermilion seed and one with seeds scattered

NEWID vs NEWSEQUENTIALID: What Each Does to Your Index

NEWID vs NEWSEQUENTIALID decides whether new uniqueidentifier keys land at random in your clustered index or in order at the end. This post loads 20,000 rows with each default, measures pages, fullness and fragmentation, and shows the limits of NEWSEQUENTIALID. It also answers what happens when you switch the default on a table that already has rows.

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