default | 易学教程

Get the default values of table columns in Postgres?

阅读更多关于 Get the default values of table columns in Postgres?

问题 I'm looking for a way to run a query to find the default values of the columns of a table in Postgres. For example, if I made a table with the following query: **Editor's note: I fixed the table definition as it has no impact on the question. CREATE TABLE mytable ( integer int DEFAULT 2, text varchar(64) DEFAULT 'I am default', moretext varchar(64) DEFAULT 'I am also default', unimportant int ); I need a query that would tell me, in some format, that the default for integer is 2, text is 'I

SQL Server: Find out default value of a column with a query

阅读更多关于 SQL Server: Find out default value of a column with a query

问题 How can I find out the default value of a column in a table using a SQL query? By using this stored procedure: sp_columns @tablename I get some information on the columns of a particular table but the default value of the columns is missing, How can I get it? 回答1: You can find the stored definition with the below (remember to adjust the column and table name to find to be ones relevant to your environment!) SELECT object_definition(default_object_id) AS definition FROM sys.columns WHERE name

How to find default browser set on android device

阅读更多关于 How to find default browser set on android device

问题 Is there any way to find out which browser is set as a default browser on android device? On android device there may be multiple browsers installed but out of which only one set as a default. I need to find it out programmatically. Thanks in advance. Early response is appreciated.. 回答1: This code may help you: Intent browserIntent = new Intent("android.intent.action.VIEW", Uri.parse("http://")); ResolveInfo resolveInfo = getPackageManager().resolveActivity(browserIntent,PackageManager.MATCH

Default value of a type at Runtime [duplicate]

阅读更多关于 Default value of a type at Runtime [duplicate]

This question already has an answer here: how to get the default value of a type if the type is only known as System.Type? [duplicate] 3 answers For any given type i want to know its default value. In C#, there is a keyword called default for doing this like object obj = default(Decimal); but I have an instance of Type (called myType) and if I say this, object obj = default(myType); it doesn't work Is there any good way of doing this? I know that a huge switch block will work but thats not a good choice. Dean Harding There's really only two possibilities: null for reference types and new

How to set a Django model field's default value to a function call / callable (e.g., a date relative to the time of model object creation)

阅读更多关于 How to set a Django model field's default value to a function call / callable (e.g., a date relative to the time of model object creation)

EDITED: How can I set a Django field's default to a function that gets evaluated each time a new model object gets created? I want to do something like the following, except that in this code, the code gets evaluated once and sets the default to the same date for each model object created, rather than evaluating the code each time a model object gets created: from datetime import datetime, timedelta class MyModel(models.Model): # default to 1 day from now my_date = models.DateTimeField(default=datetime.now() + timedelta(days=1)) ORIGINAL: I want to create a default value for a function

What is the purpose of the default keyword in Java?

阅读更多关于 What is the purpose of the default keyword in Java?

问题 An interface in Java is similar to a class, but the body of an interface can include only abstract methods and final fields (constants). Recently, I saw a question, which looks like this interface AnInterface { public default void myMethod() { System.out.println("D"); } } According to the interface definition, only abstract methods are allowed. Why does it allow me to compile the above code? What is the default keyword? On the other hand, when I was trying to write below code, then it says

how do i change default browser using c# or batch file

阅读更多关于 how do i change default browser using c# or batch file

问题 title speaks it all. 回答1: The default browser is saved as an entry in the registry key of windows. The values are saved on a protocol basis like this HKEY_CLASSES_ROOT\[protocol]\shell\open\command Where protocol can be http, https, etc. On how to access/modify registry values inside C#, you can take a look at this article 回答2: I think you will need to modify atleast two RegistryKeys and set the path to the alternative browser: HKEY_CLASSES_ROOT\http\shell\open\command HKEY_CLASSES_ROOT

How to open in default browser in C#

阅读更多关于 How to open in default browser in C#

I am designing a small C# application and there is a web browser in it. I currently have all of my defaults on my computer say google chrome is my default browser, yet when I click a link in my application to open in a new window, it opens internet explorer. Is there any way to make these links open in the default browser instead? Or is there something wrong on my computer? My problem is that I have a webbrowser in the application, so say you go to google and type in "stack overflow" and right click the first link and click "Open in new window" it opens in IE instead of Chrome. Is this

What does “default” mean after a class' function declaration?

阅读更多关于 What does “default” mean after a class' function declaration?

I've seen default used next to function declarations in a class. What does it do? class C { C(const C&) = default; C(C&&) = default; C& operator=(const C&) & = default; C& operator=(C&&) & = default; virtual ~C() { } }; It's a new C++11 feature . It means that you want to use the compiler-generated version of that function, so you don't need to specify a body. You can also use = delete to specify that you don't want the compiler to generate that function automatically. With the introduction of move constructors and move assignment operators, the rules for when automatic versions of

Is a `=default` move constructor equivalent to a member-wise move constructor?

阅读更多关于 Is a `=default` move constructor equivalent to a member-wise move constructor?

问题 Is this struct Example { int a, b; Example(int mA, int mB) : a{mA}, b{mB} { } Example(const Example& mE) : a{mE.a}, b{mE.b} { } Example(Example&& mE) : a{move(mE.a)}, b{move(mE.b)} { } Example& operator=(const Example& mE) { a = mE.a; b = mE.b; return *this; } Example& operator=(Example&& mE) { a = move(mE.a); b = move(mE.b); return *this; } } equivalent to this struct Example { int a, b; Example(int mA, int mB) : a{mA}, b{mB} { } Example(const Example& mE) = default; Example(Example&& mE) =