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I have the following code:
SELECT <column>, count(*) FROM <table> GROUP BY <column> HAVING COUNT(*) > 1;
Is there any difference to the results or performance if I replace the COUNT(*) with COUNT('x')?
(This question is related to...
Started by Andrew on
, 6 posts
by 6 people.
Answer Snippets (Read the full thread at stackoverflow):
Select count(*) from table
I'm not sure question, it was asked what....
The-difference-between-countcolumn-and-count
The major performance difference is that COUNT(*) can will return immediately, without needing to examine any rows.
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I have the following query:
select column_name, count(column_name) from table group by column_name having count(column_name) > 1;
What would be the difference if I replaced all calls to count(column_name) to count(*) ?
This question was inspired by...
Started by Bill the Lizard on
, 6 posts
by 6 people.
Answer Snippets (Read the full thread at stackoverflow):
count(*) counts NULLs and count(column) does not
[edit] added this code so that people can run) insert #bla values(null,null) select count(*),count(id),count(id2) from #bla
results 7 3 2
To clarify SQLMenace'....
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After reading the docs, it seems the the function sqlite3_column_count does all the same, but doesn't have the restrictions that sqlite3_data_count has.
Why would I ever want to use sqlite3_data_count over sqlite3_column_count? thanks!
Started by Alex Jenter on
, 3 posts
by 3 people.
Answer Snippets (Read the full thread at stackoverflow):
*/....
Sqlite3_column_count on the other hand, returns always the number in the result set for the statement pStmt.
With no results it returns 0.
Sqlite3_data_count returns the number of values (columns) of the currently executing statement.
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Count up and count down seems no difference, we can implement either one as we like. But actually what is the advantage for using count up and count down. what is the difference between them (besides that one is increment, another one is decrement)?
Started by Molly on
, 6 posts
by 6 people.
Answer Snippets (Read the full thread at stackoverflow):
If you don't know where the end is, then count-up....
On the other hand, count up also works perfectly well, with the current count telling you how much you've done.
The current count tells you how many there are left to do.
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I use Count function to get the total number or rows from a table...
Is there any difference between the two following statements?
Select Count(*) from Table
and
select Count(Id) from Table
Is there a difference between execution times...
Started by Pandiya Chendur on
, 4 posts
by 4 people.
Answer Snippets (Read the full thread at stackoverflow):
count(id) needs to null-check the column (which may be optimized away for a primary key or otherwise not-null column), so count(*) or count(1) should be prefered (unless you really want to know the number of rows with a non-null value....
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Is there a difference between the following queries, assuming there is a primary field 'id' in the table (as in speed, etc)?
SELECT COUNT(id) FROM table
vs.
SELECT COUNT(*) FROM table
Started by James Simpson on
, 6 posts
by 6 people.
Answer Snippets (Read the full thread at stackoverflow):
Have a look at Count(*) vs ....
But in for example PostgreSQL the COUNT(pkcolumnname) is much faster.
Not in MySQL, no, it has optimized the COUNT well (assuming that your id field is already a PK --which is fairly self-describing).
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I thought LINQ to SQL was tuned for performance?
The following LINQ to SQL for counting is very poor
Dim uniqueFactors As Integer = db.LargeTable.Distinct.Count
produces:
SELECT COUNT(*) AS [value] FROM [dbo].[LargeTable] AS [t0] WHERE ([t0].[ID] % @p...
Started by Coppermill on
, 4 posts
by 4 people.
Answer Snippets (Read the full thread at stackoverflow):
Since....
Selecting a rows from sysindexes (or preferably normal TSQL that perfoms ok.. .
The SELECT COUNT(*) is the only way SQL Server (and therefore LINQ) can give you an exact, up-to-date count of the rows in the table.
For larger tables.
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Started by jackiehydelover on
, 15 posts
by 4 people.
Answer Snippets (Read the full thread at fanforum):
No more post-count no subtitle! Yes, let's move our shenanigans....
Ok d'ok.
Thanks guys and gals Aye, captain! Sorry about that.
As much as I appreciate the 30+ plus posts in the last post count thread, please put all OT topics threads all turn OT.
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CREATE TABLE `names` ( `name` varchar(20) );
Assume the "names" table contains all 40 million first names of everyone living in California (for example).
SELECT count(*) as count, name FROM names GROUP BY name ORDER BY name;
How can I optimize this query...
Started by ryan on
, 3 posts
by 3 people.
Answer Snippets (Read the full thread at stackoverflow):
Do you actually have a bottleneck....
Well, what makes you think it's not already optimised? This looks like the sort of query a good database engine should be able to handle relatively easily - particularly if you've got an appropriate index on your table .
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Hi, just wondering if any of you guys use Count(1) over Count(*) and if there is a noticeable difference for SQL Server 2005 in performance? Or is this just a legacy habit that has been brought forward from days gone past?
Started by Nai on
, 9 posts
by 9 people.
Answer Snippets (Read the full thread at stackoverflow):
Select count(1)
What is the difference....
Had these URLs, which may help:
select count(*) vs.
That said, I've always used COUNT(*) .
There is no point in loading the DB engine with more work if you're .
I prefer using COUNT (1).
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