To disable adaptive join for one query, add a USE HINT to it. This post also shows a Query Store hint for code you cannot edit and the database setting that switches the feature off for everything. Each switch is tested on a small demo database and checked in the plan.
Enable Adaptive Join in SQL Server: Why It Does Not Appear
To enable adaptive join in SQL Server, the compatibility level, the database setting and the query must all agree. This post builds a demo database and probes the plan under each condition. It also corrects older advice whose statements switch the feature off.
Adaptive Threshold Rows: How an Adaptive Join Chooses
Adaptive threshold rows is the row count at which an adaptive join switches from nested loops to a hash join. This post runs two queries on WideWorldImporters, reads each threshold from the cached plan, and shows which branch ran. The first query stays below its threshold and the second goes above it.
Table or View in SQL Server: Check With OBJECTPROPERTY
To settle table or view in SQL Server, ask OBJECTPROPERTY. This post builds a table, a view, a synonym and a procedure, and reads the answers for each. It also shows a trap with other databases and a catalog query for every object.
Find Expensive Queries – SQL in Sixty Seconds #159
Earlier I wrote a blog post about SQL SERVER – List Expensive Queries – Updated March 2021. Let us learn how to Find Expensive Queries.
Maximum Columns in an Index: 32 Keys and the Way Around
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.
CHECKPOINT Covers One Database: Flush Data to Disk
CHECKPOINT covers one database, so to flush data to disk you run it in each database. A demo with two databases shows one flushed and one still dirty. A short script then flushes every database in one pass, and the post says when a flush is worth it.