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Search found 10 results on 1 pages for 'ianc'.

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• In-memory DB to perform intersects on set slices

  - by IanC

  I have a specific programming need where I need to efficiently store large sorted sets in memory, query them for ranges, and intersect them against other sets that are also queried for ranged. I am looking at Redis, but I can't see a range slice command. MongoDB can only use 1 index, so it has to perform row-level scans, whereas I wish to process…

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• Hyperthreading vs. SQL Server & PostgreSQL

  - by IanC

  I have read that hyperthreading is a "performance killer" when it comes to DBs. However, what I read didn't state which CPUs. Further, it mostly indicated that I/O was "cut to < 10% performance". That logically doesn't make sense since I/O is primarily a function of controllers and disks, not CPUs. But then no one ever said bugs made sense. …

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• Excel changing decimal places on number cells when I edit the cell's formula

  - by IanC

  I have a worksheet with thousands of number cells, all formatted "Number, 3 decimal places, use 1000 Separator ()". Starting a few days ago, if I edit a formula in any of these cells to reference another cell, Excel will change the decimal places to 14. For example, "=C$53^$B$4" = "=C$53^$B$10" will cause this. I am not aware of any settings…

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• Testing for existence using SELECT WHERE HAVING and NOT HAVING in a grouped subset

  - by IanC

  I have data on which I need to count +1 if a particular condition exists or another condition doesn't exist. I'm using SQL Server 2008. I shred the following simplified sample XML into a temp table and validate it: <product type="1"> <param type="1"> <item mode="0" weight="1" /> </param> <param…

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• T-SQL MERGE - finding out which action it took

  - by IanC

  I need to know if a MERGE statement performed an INSERT. In my scenario, the insert is either 0 or 1 rows. Test code: DECLARE @t table (C1 int, C2 int) DECLARE @C1 INT, @C2 INT set @c1 = 1 set @c2 = 1 MERGE @t as tgt USING (SELECT @C1, @C2) AS src (C1, C2) ON (tgt.C1 = src.C1) WHEN MATCHED AND tgt.C2 != src.C2…

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• Two radically different queries against 4 mil records execute in the same time - one uses brute force.

  - by IanC

  I'm using SQL Server 2008. I have a table with over 3 million records, which is related to another table with a million records. I have spent a few days experimenting with different ways of querying these tables. I have it down to two radically different queries, both of which take 6s to execute on my laptop. The first query uses a…

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• ANSI PADDING defaults question

  - by IanC

  I have SQL Server 2008 SP2. I noticed that DBs by default have Properties | Options | Miscellaneous | ANSI Padding Enabled = FALSE. However, this BOL article warns against setting it to off (no reason given). Further, this article states this feature is going to be deprecated. I have two questions: What is the "problem" with…

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• B-trees, databases, sequential inputs, and speed.

  - by IanC

  I know from experience that b-trees have awful performance when data is added to them sequentially (regardless of the direction). However, when data is added randomly, best performance is obtained. This is easy to demonstrate with the likes of an RB-Tree. Sequential writes cause a maximum number of tree balances to be…

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• Conditional PIVOT/transform problem

  - by IanC

  Hi folks I have a table with three columns, which we'll call ID1, ID2, and Value. Sample data: ID ID1 Value 1 1 0 1 2 1 1 3 1 1 3 2 1 4 0 1 4 1 1 5 0 1 5 2 2 1 2 Value is limited to 0, 1, or 2. What I need to do is pivot/transform this data into a column-based count of how…

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• When to use CTEs to encapsulate sub-results, and when to let the RDBMS worry about massive joins.

  - by IanC

  This is a SQL theory question. I can provide an example, but I don't think it's needed to make my point. Anyone experienced with SQL will immediately know what I'm talking about. Usually we use joins to minimize the number of records due to matching the left and right rows. However, under certain conditions,…

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