What could most likely cause a SQL query to run as slow as 5 minutes?

What causes SQL queries to run slow?

Poor Database Performance Tasks are taking too long. Applications running slowly or timing out. Some queries taking forever.

What are the possible reasons for slow performance in table?

Reason #2: Inefficient T-SQL Queries / CodeUsing NOT IN or IN instead of NOT EXISTS or EXISTS.Using cursors or white loop instead of INSERT… ... Using SELECT * instead of only necessary column names.Forgetting to use parenthesis when using logical OR or AND operators.Nesting of subqueries creating a complex execution plan.

How fix slow running query in SQL Server?

If you ever have a situation where query suddenly gets slower, you can try out following five steps.1Step 1: Identity Blocking for Slow Queries. The first step is to check for any blocking scenario. ... 2Step 2: Maintenance Tasks. ... 3Step 3: File growth. ... 4Step 4: TempDB Contention. ... 5Step 5: ThreadPool Wait.

What affects query speed?

Dataset size – A higher volume of data in the cluster can slow query performance for queries, because more rows need to be scanned and redistributed. You can mitigate this effect by regular vacuuming and archiving of data, and by using a predicate to restrict the query dataset.