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Inserting query result to another table hangs on “Copying to temp table on disk” on MySQL
I started the process of inserting returned results to another table. The query groups the rows in respect of indexed IDs. This causes 149,000,000 rows to be decreased to 460,000 rows.
The query ...
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1answer
2k views
Why is using a table variable more than twice as fast as a #temp table in this specific case?
I was looking at the article here
Temporary Tables vs. Table Variables and Their Effect on SQL Server Performance and on SQL Server 2008 was able to reproduce similar results to those shown there for ...
5
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1answer
554 views
Guarantee SQL Server Identity Columns that two consecutive values differ by constant increments?
I posed a question about Denali sequences here and another question about emulation of identity columns in Oracle Global Tables here.
I always thought that I could trust that identity values ...
3
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2answers
482 views
Is it bad to create many mysql temporary tables simultaneously?
I need to make heavy statistical analysis to deliver some data to users. Currently, I catch the data from mysql and process them via PHP arrays. However, mysql temporary tables are quite better ...
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3answers
18k views
What's the difference between a temp table and table variable in SQL Server?
This seems to be an area with quite a few myths and conflicting views.
So what is the difference between a table variable and a local temporary table in SQL Server?
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Why are runtimes different for a table including a primary key versus a table with a clustered unique index added after population
When I create a temporary table with a PK defined from the outset like this I get great performance in subsequent joins on that key:
create table #temp (
field1 int not null
field2 int ...
5
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1answer
343 views
Dealing with temp tables when I have not control over db variables
I have no control over things like tmp_table_size and max_heap_table_size, and so as our tables grow the time taken by queries requiring temp tables is growing geometrically.
I am wondering if there ...
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2answers
305 views
What reason is there to create a physical table for a report output?
I've noticed that for Crystal Reports made by our organization and by some of our ERA software providers have a tendency to use physical tables for their reports' data sets, rather than using a view ...
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1answer
100 views
Is there a MySQL engine or trick to avoid writing so many temp tables to disk?
I've got a web application connected to a database running MySQL.
Here's the problem: a not insignificant number of queries create temporary tables and many of the tables involved have BLOB fields. ...
