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Why are some SQL queries not performing well?
The most basic reason a query doesn’t perform well is because it’s working with too much data. Some queries just have to sift through a lot of data and can’t be helped. That’s unusual, though; most bad queries can be changed to access less data.
When does a previously-fast SQL query starts running slow?
Fortunately, it doesn’t happen that often. Look at the query plan for the query (when it is running slow). I am guessing you will find a nested loop join occurring one or more times on tables with no indexes for the join. This really slows things down.
Why do I need to run more queries than I Need?
It may also be useful to retrieve more data than you actually need if you use some type of caching in your application, or if you have another benefit in mind. Fetching and caching full objects may be preferable to running many separate queries that retrieve only parts of the object.
Why is it important to know the execution time of a query?
This metric is useful for finding queries that impact the application’s response time the most or load the server the most, but it does not tell you whether the actual execution time is reasonable for a query of a given complexity.
What’s the difference between database.query and database.soql?
Database.query can be used wherever a static SOQL query can be used, such as in regular assignment statements and for loops. Unlike inline SOQL, fields in bind variables are not supported. So the fundamental difference is the lack of support for variable binding.
Why is MY SQL Server query suddenly slow?
Sometimes query performance problems sneak into SQL Server after a software release that involves database schema or code changes, and you must hunt down the offending query and tune it. Other times, however, the performance changes for less immediately explicable reasons.