#Sqlite order by length union windows 7
Here are the contenders I am going to compare (using SQL Server 2012,, on a Windows 7 VM with 4 CPUs and 8 GB of RAM): CLR And I may re-visit this in the future to examine the impact on other metrics, but for now I'm just going to focus on duration. I'm going to compare the performance of a few solutions – and focus on the question everyone always asks: "Which is fastest?" I'm not going to belabor the discussion around *all* of the potential methods, because several have already been eliminated due to the fact that they simply don't scale. If you can't use CLR – and I know there are many of you out there who can't, due to corporate policy, the pointy-haired boss, or stubbornness – then you use one of the many workarounds that exist. The answer seems to be, almost invariably, that you should use CLR. Questionable schema design aside, in this case the comma-separated list needs to be "split" into individual values – and this is the question that frequently spurs a lot of "new" debate and commentary about the best solution to achieve just that. Teams WHERE TeamName IN ( N'Patriots', N'Red Sox', N'Bruins' ) īut since there is no array type in SQL Server, this is not how the variable is interpreted at all – it's still a simple, single string that happens to contain some commas. UserTeams (UserID, TeamID ) SELECT, TeamIDįROM dbo. This is the problem where people want to pass in a string like this: I know many people are bored of the "split strings" problem, but it still seems to come up almost daily on forum and Q & A sites like Stack Overflow. Splitting Strings : Now with less T-SQL.I’m going to leave the below content here for posterity and historical relevance, and also because some of the testing methodology is relevant to other problems aside from splitting strings, but please see some of the above references for information about how you should be splitting strings in modern, supported versions of SQL Server – as well as this post, which explains why splitting strings maybe isn’t a problem you want the database to solve in the first place, new function or not. A way to improve STRING_SPLIT in SQL Server – and you can help.Please help with STRING_SPLIT improvements.Dealing with the single-character delimiter in SQL Server's STRING_SPLIT function.Solve old problems with SQL Server’s new STRING_AGG and STRING_SPLIT functions.Comparing string splitting / concatenation methods.
#Sqlite order by length union code
(*) link provides the execution plan which suggests that current SQLite code is dumb enough to execute the redundant ordering.UPDATE: September 2nd, 2021 (Originally published July 26th, 2012.)Ī lot of things change over the course of a few major versions of our favorite database platform. And you may not be around when SQLite is upgraded or the DBMS is changed. It may work now, but you never know how long these queries will be used by the application. I think it's not good practice to use LIMIT without ORDER BY, in any DBMS. You never know what changes will be made in a future version of SQLite. Still, it's not a good idea to count on it.
So, it may appear that the two queries are producing identical results all the time. The SQLite query optimizer may (at the moment) not be very bright and do just that (no idea really, we'll have to check the source code of SQLite*). And only if the execution plan includes this ordering phase. The second query may produce the same result set but only with a primitive optimizer that doesn't understand that the ORDER BY in the subquery is redundant. The first statement will always order on StartTime and produce the first 10 rows. Second, even if there are never two rows with same StartTime, the answer is still negative. So, even the first query may not always produce the same result - with itself! First because the StartTime column may not have UNIQUE constraint.
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