A computed-column setting that saves the calculated result and refreshes it whenever the source values change, rather than working it out at read time; certain indexing and partitioning scenarios depend on it.
Read more: Microsoft Learn
In the Ultra Transcenders books
Each book explains PERSISTED in context, with comparison tables and the common traps.
Terms in this definition
- VALUES
Returns in DAX the distinct column values, or table rows, still visible after filters are applied, sometimes with an extra blank entry. CALCULATE often takes the result as a table filter.
- CRUD
Shorthand for create, read, update and delete, the four basic things you do with data. Data-plane roles in Azure Cosmos DB, for instance, authorise those operations on items.
- Partitioning
Splits a table into directories, one per value of the column or columns named in
PARTITIONED BY. Learn favours liquid clustering in most cases and keeps this technique for very large tables.
Related terms
- Computed column
A column calculated from an expression over other columns in the same row. It isn't stored unless marked
PERSISTED, and it can be indexed if the expression is precise and deterministic. - HASHBYTES
Hashes its input with an algorithm like SHA2_512 or SHA2_256 and gives back varbinary(8000). Storing that in a persisted column lets a unique constraint cover a value too large to index directly.