sql - How useful is database statistics -

-

How useful is database statistics in terms of query performance?

I did the database engine tuning at SQL Server 2004 and said that I could improve the query processing by 79% and the recommendations were made 5 figures and 1 index.

In terms of performance, in this case, how would the performance of the query be improved in terms of percentage compared to 1 index, compared to 1 index? Figures for performance queries are important without them adapting that the ordering of the path in the data is the most important. Will be efficient. Every entry table on every table is not better than a scan.

It is very important that SQL Server makes them on the fly for ad hoc queries. If you have Meritable from SELECT * where this column = 'some value' , then it will make data on ThisColumn . As the data is modified in your table, the statistics eventually become "stale", at this point the adapter starts ignoring them and actually creating bad plans. The exhibit closes a rock, those questions that used to take seconds, take a few minutes now.

For these 5 figures of these special tables - I have no way to say. Test it and see it. Remember that there is no free lunch, although the CPU takes the memory and the Io to create and maintain figures. The more of them you have the upper part; Much like indexes

Here 'which covers it.

Comments

Post a Comment

Popular posts from this blog

Pass DB Connection parameters to a Kettle a.k.a PDI table Input step dynamically from Excel -

-
Image
I have a requirement whenever I run my own kettle, dynamically took database connection parameters from an excel source Every run should go. I have an Excel column names: hostname, username, database, password. I want to pass these connection parameters to my table input stage dynamically whenever it runs the job. This is what I was trying to do. You can get it Connection parameters from the DB reading source (for example Excel or a CSV file in my example) < / Li> Store the parameters in the variable Using the variable in your connection's settings. Setting Variables Create another conversion for (you can not do it in the same conversion Uses): set variables element variable: The element that reads / writes your data creates a new connection and sets the connection parameter using $ {variable name_} Note that you will need to type in the field field in the field $ {password} Also keep in mind that this can be a security problem as the
Read more

multithreading - PhantomJS-Node in a for Loop -

-
I am trying to implement a screen-scraps application that opens a URL in which a parameter changes as it is for a loop: var data = [ '100', '101', '102', '103', '104']; (Var indexA = 0; indexA & lt; data.length; indexA ++) for {Phantom Generation ({'port': freeport}, function (pH) {ph.create page (function (page) {page.open ("http: //...++ data [index B] +" ... " , Status {console.log ("open site:" + data [index B], position); / * OLD * / indexB ++; page evaluation (function () {// page scrape and an object Return}, function {console.log (result.dataRequest); // here is the problem}); / * new and fixed * / indexB ++} first console Logs it: Open Site: 100 Success Opens Site: 101 Success B Ola Site: 102 Success Opening Site: 103 Success Opened Site: 104 Success Which is good. Data is verified in scrap HTML and from index to array Matches. So in page 101 I scrap '101 and retrieve' and pu
Read more

c++ - MATLAB .m file to .mex file using Matlab Compiler -

-
I know that it can speak as a very famous topic, but something that helps me with it Not found This scenario is: I have my functions function, no matter what's inside, it's a generic function that may depend on other toolboxes. Does. Has input and output; I want to generate the same myFun.mex function; : Lib myFun This way I get some new files: libmyfun.c libmyfun.dll Libmyfun.exp libmyfun.exports libmyfun .h libmyfun.lib Reading around and I think that Creating a myfun.cpp that is very famous is included: / * gateway function * / zero max function (ent NLHS, MXARRA * PLS [], int NRHS, CONST M Xeray * PHS []) Here is the Variable Deals * / / * code here * /} I have tried to do this and are called Regular of Max Generation: Max ('- v', 'myfun.cpp') But I get many errors, and I should say that my myfun.cpp copy / Paste Function is where I have a lot of doubts ... especially on input / output management. My q
Read more