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SELECT a column_with_null, NVL(a, 'N/A') column_without_null FROM (SELECT NULL a FROM DUAL); COLUMN_WITH_NULLCOLUMN_WITHOUT_NULL(null)N/A NVL is useful to compare two values which can contain NULLs : SELECT CASE WHEN a = b THEN 1 WHEN a <> b THEN 0 else -1 END comparison_without_n...

If the first parameter is NOT NULL, NVL2 will return the second parameter. Otherwise it will return the third one. SELECT NVL2(null, 'Foo', 'Bar'), NVL2(5, 'Foo', 'Bar') FROM DUAL; NVL2(NULL,'FOO','BAR')NVL2(5,'FOO','BAR')BarFoo

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...

To navigate to a newest page, we can use the Navigate() method from the frame. contentRoot.Navigate(typeof(MyPage), parameter); where contentRoot is the Frame instance and MyPage a control inheriting from Page In MyPage, the OnNavigatedTo() method will be called once the navigation will complet...

A function that extends the functionality of the array by creating an object oriented remove function. // Need to restrict the extension to elements that can be compared. // The `Element` is the generics name defined by Array for its item types. // This restriction also gives us access to `index(...

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MQTT(Message Queue Telemetry Transport) is a Publish-Subscribe based "lightweight" messaging protocol for use on top of the TCP/IP stack. It is quite useful for connections with remote locations where a small code footprint is required and/or network bandwidth is at a premium. Ther...

import cv2 def canny_webcam(): "Live capture frames from webcam and show the canny edge image of the captured frames." cap = cv2.VideoCapture(0) while True: ret, frame = cap.read() # ret gets a boolean value. True if reading is successful (I think). frame ...

An input port can be created in many ways, but usually the method starts with open-input-. String port You can use a string as a port using open-input-string. It will create a port that will be able to read from the string. (define p (open-input-string "(a . (b . (c . ()))) 34")) ...

Reading from an input port can be done in many ways. We can use the read method used by the REPL. It will read and interpret space separated expressions. Taking the example from the string port above. We can read from the port like this: (define p (open-input-string "(a . (b . (c . ()))) 3...

import pyglet audio = pyglet.media.load("audio.wav") audio.play() For further information, see pyglet

There is a particular syntax that allow us to write cons cell in a more compact way than using the cons constructor. A pair can be written as such: '(1 . 2) == (cons 1 2) The big difference is that we can create pairs using quote. Otherwise, Scheme would create a proper list (1 . (2 . '())). T...

The data in the pair can be accessed with utility functions. To access the car, we have to use the car function. (car (cons a b)) > a Also we can verify the following equality: (eq? a (car (cons a b))) > #t

To access the cdr, we have to use the cdr function. (cdr (cons a b)) b Also we can verify the following equality: (eq? b (cdr (cons a b))) #t

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.

A enum declares a set of ordered values - the typedef just adds a handy name to this. The 1st element is 0 etc. typedef enum { Monday=1, Tuesday, Wednesday } WORKDAYS; WORKDAYS today = Monday;//value 1

Here’s an example vector asset which we’re actually using in AppCompat: res/drawable/ic_search.xml <vector xmlns:android="..." android:width="24dp" android:height="24dp" android:viewportWidth="24.0" android:viewportHeig...

Here is a simple VectorDrawable in this vectordrawable.xml file. <vector xmlns:android="http://schemas.android.com/apk/res/android" android:height="64dp" android:width="64dp" android:viewportHeight="600" android:viewportWidth=&quot...

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