Search DaniWeb - exists

Re: Differential Directory, indexing method 6 Days Ago by xrjf I've just made an update because some records weren't being added properly. The issue was that the form didn't take into account that the register field (in the call to DiDi) is passed by reference. Re: Differential Directory, indexing method 4 Days Ago by noahevans This is a brilliant explanation of how Differential Directory (DiDi) indexing works — very efficient and elegant. The idea of storing only the first differing bit between keys reminds me of how we optimize systems for speed and memory, much like how some tech repair services streamline diagnostics. At FixnVibe, our approach to mobile phone … Differential Directory, indexing method 1 Week Ago by xrjf … the index is in memory, it determines whether the key exists or not. * The index is always sorted and therefore requires… Re: Differential Directory, indexing method 1 Week Ago by rproffitt DiDi appears to be some China based UBER service but then again I can't find a question or much else to discuss here. Re: Differential Directory, indexing method 1 Week Ago by xrjf About DiDi DiDi (Differential Directory) was originally developed as part of my thesis project in the early 1990s. The name bears no relation to the more recent Chinese ride-sharing company. At the time, DiDi was a novel approach within its academic context, but a change in legislation unfortunately led to the closure of the school and the … Re: Differential Directory, indexing method 1 Week Ago by xrjf For example, as Donald Knuth points out in The Art of Computer Programming, the theoretical lower bound for comparison-based sorting algorithms is K × log₂(N). I developed a very simple method that matches this performance. However, DiDi goes far beyond: its performance is proportional to K × (maximum key length), regardless of the number of … Re: Differential Directory, indexing method 1 Week Ago by xrjf As an illustration, consider the theoretical lower bound for comparison-based sorting, as stated by Donald Knuth in The Art of Computer Programming: K × log₂(N). I developed a simple method that matches this limit. For example, to sort the list {2, 5, 7, 1, 4, 3, 8, 6}: Sort pairs: (2, 5) → [1] (1, 7) → [2] (3, 4) → [3] (6, 8) → [4] Merge… Re: Differential Directory, indexing method 1 Week Ago by xrjf "Just to clarify a previous mistake: the efficiency should be K × N × log₂(N), not K × log₂(N) as I initially wrote." Re: How to connect to the Pinterest API using PHP? 1 Month Ago by Dani Oh, it looks as if the tutorial was for the old DaniWeb API that no longer exists. The [DaniWeb Connect API](https://www.daniweb.com/connect/developers) is also OAuth-based and has some of its own documentation. Re: EXISTS operator in SQL ? 11 Years Ago by deceptikon `exists` looks for the first match in the subquery. If it returns true for any of the matches in the outer query, the `where` clause succeeds and that record will be selected. Re: EXISTS operator in SQL ? 11 Years Ago by deceptikon … IN can not be necessarily used as a replacement from Exists, or reverse ? `in` can be used as a replacement… `b` will *always* contain at least one record, and the `exists` test will *always* evaluate to true. Therefore you'll *always… to products that are tied to the customer, and the `exists` works as intended. `in` works in a different manner:… Re: EXISTS operator in SQL ? 11 Years Ago by deceptikon … of those customers to send survey emails. You could use `exists` to retrieve that list and exclude customers that didn't… c.ID, c.Name, c.Email from Customers c where exists (select * from SurveyEnrolement se where se.CustomerID = c.ID); Not… just think it may be a more clear example of `exists`. EXISTS operator in SQL ? 11 Years Ago by HunainHafeez i almost spent 3 hours on EXISTS operation, used in SQL especially with subqueries, i got its … *TABLE GEOGRAPHY* regionName----storeName SELECT SUM(Sales) FROM Store_Information WHERE EXISTS (SELECT * FROM Geography WHERE Region_Name = 'West'); Re: EXISTS operator in SQL ? 11 Years Ago by HunainHafeez but what i concluded is that EXISTS can be handy in situations like IF EXISTS (SELECT ...... from ....... where) Begin DO SOMETHING BECAUSE IT's OBVIOUS THAT TABLE HAS ROWS END correct me if i'm wrong ? Re: EXISTS operator in SQL ? 11 Years Ago by deceptikon … boolean value TRUE, ok ? It will select a matching record. `exists` evaluates to a boolean based on the presence of any… words). I think the issue here may be less about `exists` in particular and more about relational logic in general. Re: EXISTS operator in SQL ? 11 Years Ago by HunainHafeez great replies (Y) so is it correct to say that IN can not be necessarily used as a replacement from Exists, or reverse ? because with IN you can get result set and can match them in WHERE clause but not true for EXISTS since it returns only TRUE OK ? Re: EXISTS operator in SQL ? 11 Years Ago by HunainHafeez … products where prodCategory= 'Consumer electronics') // using Exists Select customers.cus_id, customers.cusName from customers where exists (select cus_id from products where prodCategory… Re: EXISTS operator in SQL ? 11 Years Ago by HunainHafeez let's put it in simple words, the subquery in this code will return on a boolean value TRUE, ok ? where exists (select * from SurveyEnrolement se where se.CustomerID = c.ID); returns true so if it becomes true then it's like a GO signal for Outer query and that get execute ? right ? Re: EXISTS operator in SQL ? 11 Years Ago by JorgeM … test to see if there is a TRUE, meaning record exists. So in deceptikon's example...it will return all records… Re: Need help checking if a file exists 12 Years Ago by yup790 .exists down't work The commented code doesn't work Would it work to write a copy of the exists method in the class Re: Need help checking if a file exists 12 Years Ago by JamesCherrill > .exists down't work .exists does work. It's been in the Java API forever, … file / folder exists 14 Years Ago by darkseid …; " succesfully!", MsgBoxStyle.Information, "Information") ElseIf Directory.Exists(lItem.Text) Then fSource = leftCBselect.Text & lItem.Text Me… folder copy both work but not if add the file.exists / folder.exists lines. if i put a msgbox instead of the… Check if INPUT value Exists 14 Years Ago by jonnypixel …a fadeIN div to say it "already exists" otherwise fadeIN a div to say &… basically if the tag "People" exists in the MYSQL table then i want the …#i2 to fade in and say "Already exists!"[/I][/B][/INDENT] My code is below…strong>Failed:</strong> The keyword already exists.</p> </div> </form… Help with sql query involving not exists 12 Years Ago by cmstoner … w, taggings t WHERE t.taggable_type = 'Workbook' AND NOT EXISTS (SELECT distinct w.name FROM taggings WHERE taggings.taggable_type = 'Workbook…datasources d, taggings t WHERE t.taggable_type = 'Datasource' AND NOT EXISTS (SELECT d.name FROM taggings WHERE taggings.taggable_type = 'Datasource' AND… Checking whether cstudentCode exists 12 Years Ago by prateek29chandra … combobox nd click save button it should check if id exists in table thn only it should update the result. if… two things to be done 1- if id exists or not , 2- if exists it should update it. how can i acheive… as how can i check if student id exists in the above table //if exists update the table, if not thn error Check if a temp table exists and drop the table 11 Years Ago by Nebil … the it,since "the temptable already exists" arises if you want to perform…. "DROP TABLE IF EXISTS LIKE 'prtempTable%'" "DROP TABLE IF EXISTS LIKE '%prtempTable%'" "…;DROP TABLE IF EXISTS WHERE TABLE LIKE 'prtempTable%'"… Python code to check if the file exists within Android Internal Storage 9 Years Ago by Karthik_4 …check whether the **recording** (recordingX.mp3) actually exists with the same name within the specific directory or…>>> print os.path.exists('sdcard/Maverick') False >>> print os.path…; print os.path.exists('sdcard0/Maverick') False >>> print os.path.exists('sdcard0/Maverick/') False… Trying to use List.Exists in C# 16 Years Ago by VernonDozier …> public void AddChild(Node childNode) { if(!this.children.Exists(childNode)) this.children.Add(childNode); } [/code] Line 3… me an error. I am not using [ICODE]Exists[/ICODE] right. The example code I have seen …a boolean function that you pass to the [ICODE]Exists[/ICODE] function, but those functions all have certain … Re: determining if an SQL database exists, etc. 16 Years Ago by mail2saion …CHECK DB EXIST OR NOT: [CODE]if NOT exists(select 1 from master.dbo.sysdatabases where name = …'yourDB') begin print 'DB does not exists'; end[/CODE] Database is accessible: [CODE]Begin Declare… Else Print 'Invalid Database'; End[/CODE] Table Exists/Not: [CODE]IF EXISTS (SELECT * FROM sys.objects WHERE object_id =… Conditional insert using WHERE NOT EXISTS 16 Years Ago by nav33n … ) SELECT name, age, postcode, city FROM b WHERE NOT EXISTS ( SELECT * FROM c WHERE counter = ( SELECT c_id FROM…, postcode, city FROM b where counter = 1 WHERE NOT EXISTS ( SELECT * FROM c WHERE counter = ( SELECT c_id …, postcode, city FROM b where counter = 1) WHERE NOT EXISTS ( SELECT * FROM c WHERE counter = ( SELECT c_id FROM…