Why does one SQL query take longer than the other?

Why does one SQL query take longer than the other?

I have a SQL database server and 2 databases under it with the same structure and data. I run the same sql query in the 2 databases, one of them takes longer while the other completes in less than 50% of the time. They both have different execution plans.

What happens if you have two databases on the same server?

The fact that you have two databases on same server and with same data set (as you said) does not ensure same execution plan. mdf and ldf files (for each database) are on different drives. If one drives is faster, that database will run the query faster too. stalled statistics.

What can I do to make SQL query run faster?

They both have different execution plans. The things i have already tried are – rebuild & reorganize index on the table (tblRRMHistSimShifts – this table has over 2 million records), checked for locks or other background processes or errors on server, Max degree of parallelism for the server is 0.

Why is my delete query taking too much time?

You could be blocked by another session (most likely). Before you delete you should make sure noone else is locking the rows, eg: issue SELECT NULL FROM tablename WHERE colname=:value FOR UPDATE NOWAIT,

How long does it take to delete a query in SQL?

First check is how fast is locate this row in SELECT query. I run: The result: less then 2 seconds. I read about this issue in this thread. I took the selected answer and extract a check list from it. See my answers inside. deleting a lot of records – This query deletes exactly 1 row.

Why do you get different query plans for different executions?

Are you getting different query plans for different executions (you may need to capture a query plan from your initial benchmarks and compare it to the current plan or you may need to increase your AWR retention to retain query plans for a few months in order to see this).

Why does SQL query join so many tables?

It might be you have a lot of data and as the where clause is being run at the end of the query process you are joining huge volumes of data before filtering it.

Why is this simple join taking so long?

It’s taking about 11 minutes 30 seconds to run. DESCRIBE returns this analysis: It seems to bottleneck at the “copying to tmp table” stage.

How long does it take to join a table in SQL?

After joining 12 tables, there was no significant change in query execution time. By the time I had joined the 13th table the execution time jumped to a 1 second; 14th table 4 seconds, 15th table 20 s, 16th 90 seconds. Keijro’s suggestion to use a correlated subqueries instead of joins e.g.

What happens when you merge two queries in Excel?

The first query is a primary table and the second query is a related table. The related table contains all rows that match each row from a common column value in the primary table. For more information, see Merge queries. Append Creates a new query that contains all rows from a first query followed by all rows from a second query.

How to combine multiple SQL queries into a single one?

For help clarifying this question so that it can be reopened, visit the help center . Closed 9 years ago. I have these multiple sql queries that I want to bundle together into one single query, so that I can avoid sending multiple requests to the database from my application ( I want to receive all of these data in one single shot) :

Why is SQL Server not using the geospatial index?

In both instances, query plans indicate that they’re starting with a scan of the geospatial index, so it’s not the problem that sometimes happens, that SQL Server can’t figure out it’s supposed to use the index in question. My assumption is that it has something to do with how the geospatial index is laid out.

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.

How to fix slow queries in Stack Overflow?

In my experience, most slow queries can be tuned up via code or Index, instead of adding a NO LOCK hint that may get you modified or old result sets, depending of your transactions. Thanks for contributing an answer to Stack Overflow!

How can I Make my SQL query run faster?

The way to make a query run faster is to reduce the number of calculations that the software (and therefore hardware) must perform. To do this, you’ll need some understanding of how SQL actually makes calculations.

Which is an example of a slow SQL query?

Joins: If your query joins two tables in a way that substantially increases the row count of the result set, your query is likely to be slow. There’s an example of this in the subqueries lesson.

When to use having and where clauses in the same query?

Use HAVING and WHERE Clauses in the Same Query (Visual Database Tools) In some instances, you might want to exclude individual rows from groups (using a WHERE clause) before applying a condition to groups as a whole (using a HAVING clause).

How to get estimated completion time of SQL Server?

In this tip, we will explore a very simple script to get the estimated amount time which SQL Server is going to take to complete database Backup or Restore. You may find the below script very useful when we are dealing with the very large database.

Why does SQL Server take so long to scan a table?

This procedure might take much longer than scanning the table itself: “Table Scan”. but based on the statistics that sql-server has, in such situations, it might not use your index at all.

Why does SQL SELECT take so long to execute?

so first of all check the Execution Plan to see if the index is used at all. if yes or no both, alter your index to include all columns that you are selecting. say like: in this case Look Up will not be needed, and your query will execute so much faster. Its the sub selects in your column selection that is causing the slow return.

When to use% s in place of query?

The URL with %s in place of query field should include the web address for the search engine’s results page, and use %s where the query would go. If you want to know more click this website (that’s…

Why does my SQL Server keep running slow?

I’ve concluded (perhaps incorrectly) from these little experiments that the reason for the slow-down is due to how SQL’s cached execution plan is set up — when the query is a little different, it has to create a new execution plan. This can be easily tested. SET STATISTICS TIME ONwill show you the compile vs. execution time.

How to know how long SQL-SP is taking?

You can clear the cache out using: But only do this on a dev/test db server, not on production. Then run the query, record the stats (e.g. from profiler). Clear the cache again. Run the SP and compare stats. 1) When you run the query for the first time it may take more time.

Why does SQL take 15 minutes to run?

There are several possible fixes, including adding WITH RECOMPILE to your stored procedure which works about half the time.