Tutorial by Examples: co

SELECT 1 NUM_COLUMN, 'foo' VARCHAR2_COLUMN from DUAL UNION ALL SELECT NULL, NULL from DUAL; NUM_COLUMNVARCHAR2_COLUMN1foo(null)(null)

SELECT 3 * NULL + 5, 'Hello ' || NULL || 'world' from DUAL; 3*NULL+5'HELLO'||NULL||'WORLD'(null)Hello world

SELECT COALESCE(a, b, c, d, 5) FROM (SELECT NULL A, NULL b, NULL c, 4 d FROM DUAL); COALESCE(A,B,C,D,5)4 In some case, using COALESCE with two parameters can be faster than using NVL when the second parameter is not a constant. NVL will always evaluate both parameters. COALESCE will stop a...

COMMENT ON TABLE table_name IS 'this is student details table';

COMMENT on TABLE student IS NULL; Comment will be removed with above statement execution.

private bool navigateFlag = false; protected async override void OnNavigatingFrom(NavigatingCancelEventArgs e) { base.OnNavigatingFrom(e); if (!navigateFlag) { e.Cancel = true; var dialog = new MessageDialog("Navigate away?", Confir,); ...

NSMutableAttributedString * string = [[NSMutableAttributedString alloc] initWithString:@"firstsecondthird"]; [string addAttribute:NSForegroundColorAttributeName value:[UIColor redColor] range:NSMakeRange(0,5)]; [string addAttribute:NSForegroundColorAttributeName value:[UIColor greenColo...

Dependenct Injection Intro An application is composed of many objects that collaborate with each other. Objects usually depend on other objects to perform some task. When an object is responsible for referencing its own dependencies it leads to a highly coupled, hard-to-test and hard-to-change code...

Maybe Maybe is an applicative functor containing a possibly-absent value. instance Applicative Maybe where pure = Just Just f <*> Just x = Just $ f x _ <*> _ = Nothing pure lifts the given value into Maybe by applying Just to it. The (<*>) function applies...

It is a bad practice to block on async calls as it can cause deadlocks in environments that have a synchronization context. The best practice is to use async/await "all the way down." For example, the following Windows Forms code causes a deadlock: private async Task<bool> TryThis()...

The easiest way to record a macro is the button in the lower left corner of Excel looks like this: When you click on this you will get a pop-up asking you to name the Macro and decide if you want to have a shortcut key. Also, asks where to store the macro and for a description. You can choose any ...

File: /etc/resolv.conf contains a list of DNS servers for domain name resolution Sample contents of the file: nameserver 8.8.8.8 # IP address of the primary name server nameserver 8.8.4.4 # IP address of the secondary name server In case internal DNS server you can validate if this server reso...

IMPORTANT This is just an example code, do not use in production. In order to download an header chain we have to send a getHeaders message. In this example we will require as much as possible headers after the 40000th one.The peer will respond with batch of 2000 headers so, we have to take the la...

This should always be your initial fix. A good policy is to decompile the database before each release. Create a decompile shortcut. This loads the database with a "/decompile" switch. Right Click your Database File. Select Copy Right Click in the explorer window and select &quot...

If your crashes are random or sporadic, then do this step. If your crashes occur every single time you run the database, then this step won't fix the issue (although bad memory may be the reason why the corruption occurred in the first place). Use a memory tester that boots outside the operating sy...

When you develop a C++ program, the next step is to compile the program before running it. The compilation is the process which converts the program written in human readable language like C, C++ etc into a machine code, directly understood by the Central Processing Unit. For example, if you have a...

function doGet(e){ var serveFile = e.parameter.servefile; var id = e.parameter.id; if(serveFile) { return downloadFile(id); // and Hyde } return HtmlService.createHtmlOutputFromFile('form.html'); // Jekyll } function fetchFromGoogleDrive() { // Jekyll va...

You can create new commands via php artisan make:command [commandName] So this will create [commandName] command class inside app/Console/Commands directory. inside this class you will find protected $signature and protected $description variables, it represents name and discription of your comma...

Retrieve AD Computer Get-ADComputer -Identity "JohnLaptop" Retrieve All Properties Associated with Computer Get-ADComputer -Identity "JohnLaptop" -Properties * Retrieve Select Properties of Computer Get-ADComputer -Identity "JohnLaptop" -Properties * | Select-O...

//fill column A with solid red color from hex worksheet.Column(1).Style.Fill.PatternType = ExcelFillStyle.Solid; worksheet.Column(1).Style.Fill.BackgroundColor.SetColor(ColorTranslator.FromHtml("#FF0000")); //fill row 4 with striped orange background worksheet.Row(4).Style.Fill.Patte...