null

问题 As it currently stands, this question is not a good fit for our Q&A format. We expect answers to be supported by facts, references, or expertise, but this question will likely solicit debate, arguments, polling, or extended discussion. If you feel that this question can be improved and possibly reopened, visit the help center for guidance. Closed 6 years ago . This is a style question for C and C++. Do you prefer void f() { const char * x = g(); if (x == NULL) { //process error } // continue

问题 Consider the update: UPDATE table1 SET c1 = NVL(( SELECT d1 FROM table2 WHERE table1.id = table2.id ), 0), c2 = NVL(( SELECT d2 FROM table2 WHERE table1.id = table2.id ), 0) The NVL function handles the case where the sub-select returns no rows. Is there a good way to rewrite this (without repeating the sub-select) using this type of syntax: UPDATE table1 SET (c1,c2) = ( SELECT d1, d2 FROM table2 where table1.id = table2.id ) such that the case where the sub-select returns now rows is handled

问题 Consider the update: UPDATE table1 SET c1 = NVL(( SELECT d1 FROM table2 WHERE table1.id = table2.id ), 0), c2 = NVL(( SELECT d2 FROM table2 WHERE table1.id = table2.id ), 0) The NVL function handles the case where the sub-select returns no rows. Is there a good way to rewrite this (without repeating the sub-select) using this type of syntax: UPDATE table1 SET (c1,c2) = ( SELECT d1, d2 FROM table2 where table1.id = table2.id ) such that the case where the sub-select returns now rows is handled

问题 can someone explain me why NSUserDefaults is returning me "nil" for an object that is not? I have a view with some settings for a game, there is a textfield in where user can write his name. I save this name in NSUserDefaults and put it as placeholder for the other times user enter this view. I set the object like that: NSUserDefaults *defaults=[NSUserDefaults standardUserDefaults]; NSString *fieldName = _nameField.text; [defaults setObject:fieldName forKey:@"playerName"]; [[NSUserDefaults

问题 This question already has an answer here : attempt to compare nil with number Corona (1 answer) Closed 6 years ago . hey guys i am about to finish my game i am a indie developer and i i am trying to finish my app in corona sdk and i keep getting this annoying error message. The message is get is " Attempt to compare nil with number restart.lua 9 " i don't have a clue how to fix this i try every thing but nothing works. when i run my code and i die for the first time and restart the game it

问题 I have a problem regarding to a SUM function in sql that gives NULLs, thus brakes all the structure of the table: (x-month,y-cities,value-Nettotal) but i get wrongly arranged values according to a y-cities, because there are no free spaces, i mean 0 values, here is the screenshot to make it more clear: and the link to a question i asked before but couldnt get a clear answer: group by cities So what I and Dave DuPlantis have wrote so far is: the query: <cfquery name="GET_SALES_TOTAL"

问题 I have a problem regarding to a SUM function in sql that gives NULLs, thus brakes all the structure of the table: (x-month,y-cities,value-Nettotal) but i get wrongly arranged values according to a y-cities, because there are no free spaces, i mean 0 values, here is the screenshot to make it more clear: and the link to a question i asked before but couldnt get a clear answer: group by cities So what I and Dave DuPlantis have wrote so far is: the query: <cfquery name="GET_SALES_TOTAL"

问题 This question already has answers here : Comparing with NULL values (5 answers) Closed 3 years ago . I have the following query: SELECT * FROM table WHERE orderdate >= "2015-12-01" AND orderdate <= "2015-12-31" AND values > 0 AND orders <> 'Returned' The problem is that the query doesn't return the rows where the orders column is NULL and I can't figure out why. 回答1: This is the sql language. Mysql doesn't consider NULL as value. So if you want to include NULL we must specify that. SELECT *

问题 I have two classes: A UIViewController and a class that's subclassing NSObject that acts as a downloading helper class called OfficesParser. OfficesParser is using ASIHTTPRequest and I set the delegate for the download requests to be my UIViewController. EDIT : Interface for the UIViewController: @interface OfficesViewController : UIViewController <UITableViewDelegate, UITableViewDataSource, ASIHTTPRequestDelegate> { OfficesParser *officesParser; } @property (nonatomic, retain) OfficesParser