Sql updating table definition problems with using carbon dating
The past few chapters have focused on basic query techniques, all centered around the task of getting data out of a database.
This chapter turns the tables, and focuses on the following three topic areas: For ease in finding them when you need them, recipes in this chapter have been grouped by topic: all the insertion recipes come first, followed by the update recipes, and finally recipes for deleting data. It begins with the simple problem of inserting a single row.
This includes statistics created using the CREATE STATISTICS statement, single-column statistics created when AUTO_CREATE_STATISTICS is on, and statistics created for indexes.
For more information about AUTO_CREATE_STATISTICS, see ALTER DATABASE SET Options (Transact-SQL).
We recommend not updating statistics too frequently because there is a performance tradeoff between improving query plans and the time it takes to recompile queries. UPDATE STATISTICS can use tempdb to sort the sample of rows for building statistics.
Transact-SQL Syntax Conventions -- Syntax for SQL Server and Azure SQL Database UPDATE STATISTICS table_or_indexed_view_name [ ] [ WITH [ FULLSCAN [ [ , ] PERSIST_SAMPLE_PERCENT = ] | SAMPLE number [ [ , ] PERSIST_SAMPLE_PERCENT = ] | RESAMPLE [ ON PARTITIONS ( [, …n] ) ] | is not specified, the query optimizer updates all statistics for the table or indexed view.
A view contains rows and columns, just like a real table.
Updating statistics ensures that queries compile with up-to-date statistics.
However, updating statistics causes queries to recompile.
To view all indexes for a table or view, you can use sp_helpindex.
FULLSCAN Compute statistics by scanning all rows in the table or indexed view. The actual percentage or number of rows the query optimizer samples might not match the percentage or number specified.