The maximum columns in an index is 32 key columns, and a second limit on key size can stop an index earlier. This post builds a 40 column table, shows the error for a 33rd key column, and adds included columns to get around it. It also shows the 900 and 1,700 byte key limits and tests statistics on 33 and 40 columns.
sp_updatestats and Disabled Indexes: What Gets Updated
sp_updatestats and disabled indexes: the procedure updates statistics on disabled nonclustered indexes and skips a table whose clustered index is disabled. This post proves both, times the cost of disabled indexes against dropped ones on a million rows, and generates a targeted update that skips them.
JOIN Elimination in SQL Server: When a Table Drops Out
JOIN elimination removes a joined table from the plan when the query does not need it. This post proves it with STATISTICS IO, then tests nine variations to show when it applies and when it does not, including a foreign key that has lost its trust.
sp_autostats: See and Undo Automatic Statistics Updates
The sp_autostats procedure shows and changes the automatic statistics update setting of one table, one index or one statistic. This post turns the setting off for a table, flips it back for one index, undoes it, and shows that the database level setting and the statistics themselves are untouched.
SQL SERVER – What is Logical Read?
A logical read requests a database page through the buffer cache. A customer asked about that measure after my STATISTICS IO video.
Scan Count Zero in STATISTICS IO: What the Number Means
Scan count zero in STATISTICS IO is not an error and not a free read. This post runs nine small queries and shows what 0, 1, 2 and 5 mean, why a unique lookup counts as zero, and why logical reads are the number to compare.
SET STATISTICS TIME ON – SQL in Sixty Seconds 139
Do you know how long your query took to execution? Well, let us learn that today in SQL in Sixty Seconds. We will discuss SET STATISTICS TIME ON.