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问题 I'm trying to do a join on 2 tables in Zend, using the DbTable / model / mapper structure. If, in my mapper, I do this: $select = $this->getDbTable()->select(Zend_Db_Table::SELECT_WITH_FROM_PART) ->setIntegrityCheck(false) ->join('images', 'images.oldFilename = availablePictures.filename') ->where('images.ref IS NOT NULL'); $resultSet = $this->getDbTable()->fetchAll( $select ); it works like a charm, but if I try the same thing with IS NULL instead of NOT NULL, I get nothing where I should

问题 This is probably super simple but I just can not find the answer. I import data using GeoPandas from a shape file. Turn that into pandas DataFrame . I have a object field with three letter codes and None values for missing data. How do I change None 's to something like "vcv" in pandas? I tried this sala.replace(None,"vcv") got this error 2400 "strings or regular expressions, you " 2401 "passed a" -> 2402 " {0!r}".format(type(regex).__name__)) 2403 return self.replace(regex, value, inplace

问题 I'm trying to select from XML that has a null as one of the attributes. Instead of returning a null, it returns a 0. What am I doing wrong? See code below to replicate: declare @a xml select @a = '<TestSet xmlns:xsi="http://www.w3.org/2001/XMLSchema-instace"> <Element> <Property1>1</Property1> <Property2>1</Property2> </Element> <Element> <Property1 xsi:nil="true" /> <Property2>2</Property2> </Element> <Element> <Property1>3</Property1> <Property2>3</Property2> </Element> </TestSet>' select

问题 I just learned that dereferencing null in C and C++ can sometimes produce undefined results. This is very intriguing to me, like all bizarre programming behaviors (I once had someone tell me that they debugged "corrupt RAM - program does not run as written" in a legitimate production environment). Because I'm primarily a Java developer, I was wondering if it's possible for this to happen in that language as well? The JLS is not specific on how the null reference is implemented (3.10.7, 4.1,

问题 I want to assign a null value to a variable called $dec , but it gives me errors. Here is my code: import-module activedirectory $domain = "domain.example.com" $dec = null Get-ADComputer -Filter {Description -eq $dec} 回答1: These are automatic variables, like $null , $true , $false etc. about_Automatic_Variables , see https://technet.microsoft.com/en-us/library/hh847768.aspx?f=255&MSPPError=-2147217396 $NULL $null is an automatic variable that contains a NULL or empty value. You can use this

问题 In SQL Server 2008, I'm using MERGE. Everything is fine except that I have 2 nullable columns. If I pass a null value and the target isn't null, MERGE doesn't see a difference (evals against null = false per BOL). If I use IsNull on both sides (source & target) that works, but has the issue of potentially mis-evaluating a value. What I mean by the last statement is, if I say: WHEN MATCHED AND NOT (IsNull(tgt.C, 0) = IsNull(src.C, 0)) THEN then if tgt.C is null and src.C = 0, no update will be

问题 This question already has answers here : Closed 6 years ago . Possible Duplicate: How to check if String is null I need to be able to check for a null value, only, inside a string. The best method I am currently aware of is String.IsNullOrEmpty() , which does not fit what we are trying to do ( string.empty values are allowed, nulls are not). Does anyone have any suggestions? 回答1: just compare your string to null bool stringIsNull = mystring == null; here's an extension method for you public

问题 I am trying to use inline if condition as follows: topDisplay.text = topDisplay.text!.rangeOfString(".") ? "Sth for true" : "Sth for false" The idea here is if there is "." in the topDisplay.text! then do something, if not, do something else. The method, rangeOfString, returns nil if no "." is found. So I am wondering is it possible to check nil within inline condition expression. ((btw, you might find out that I am trying to add "." button for calculator assignment in Stanford's online

问题 If you have two overloaded methods like so: public void methodName(File file){} public void methodName(String string){} If you try to call methodName with null you will get an error saying that it's ambiguous which is understandable because it doesn't know which method to do. I know that you can just cast the null: methodName((String) null) but how can I create a method specifically to handle the situations where you call methodName(null) ? Something like this: public void methodName(null

问题 So I'm trying to create a report that generates the best male and/or best female nominations/winners. However when I run my select I'm getting all the movies who do not have winners or nominations. Having trouble figuring out how to get rid of the nulls. Here's my code. This is in Oracle by the way. /*Oscar Nominations for Best Actor Report */ SELECT movie.MVYEAR as "Movie Year", movie.MVTITLE as "Movie Title", star.STARNAME as "Star Name", movstar.BESTM as "Best Male", movstar.BESTF as "Best