Tutorial by Examples: e

The unary negation (-) precedes its operand and negates it, after trying to convert it to number. Syntax: -expression Returns: a Number. Description The unary negation (-) can convert the same types / values as the unary plus (+) operator can. Values that can't be converted will evaluat...

The bitwise NOT (~) performs a NOT operation on each bit in a value. Syntax: ~expression Returns: a Number. Description The truth table for the NOT operation is: aNOT a01101337 (base 10) = 0000010100111001 (base 2) ~1337 (base 10) = 1111101011000110 (base 2) = -1338 (base 10) A bit...

The logical NOT (!) operator performs logical negation on an expression. Syntax: !expression Returns: a Boolean. Description The logical NOT (!) operator performs logical negation on an expression. Boolean values simply get inverted: !true === false and !false === true. Non-boolean val...

DynamoDB is a fully managed service provided by AWS. It does not need to be installed or configured. AWS is responsible for all administrative burdens of operating, scalling and backup/restore of the distributed database.

All DATEs have a time component; however, it is customary to store dates which do not need to include time information with the hours/minutes/seconds set to zero (i.e. midnight). Use an ANSI DATE literal (using ISO 8601 Date format): SELECT DATE '2000-01-01' FROM DUAL; Convert it from a string ...

Convert it from a string literal using TO_DATE(): SELECT TO_DATE( '2000-01-01 12:00:00', 'YYYY-MM-DD HH24:MI:SS' ) FROM DUAL; Or use a TIMESTAMP literal: CREATE TABLE date_table( date_value DATE ); INSERT INTO date_table ( date_value ) VALUES ( TIMESTAMP '2000-01-01 12:00:00' ); Oracl...

In Oracle a DATE data type does not have a format; when Oracle sends a DATE to the client program (SQL/Plus, SQL/Developer, Toad, Java, Python, etc) it will send 7- or 8- bytes which represent the date. A DATE which is not stored in a table (i.e. generated by SYSDATE and having "type 13" ...

Use TO_CHAR( date [, format_model [, nls_params]] ): (Note: if a format model is not provided then the NLS_DATE_FORMAT session parameter will be used as the default format model; this can be different for every session so should not be relied on. It is good practice to always specify the format mod...

When Oracle implicitly converts from a DATE to a string or vice-versa (or when TO_CHAR() or TO_DATE() are explicitly called without a format model) the NLS_DATE_FORMAT session parameter will be used as the format model in the conversion. If the literal does not match the format model then an excepti...

When SQL/Plus or SQL Developer display dates they will perform an implicit conversion to a string using the default date format model (see the Setting the Default Date Format Model example). You can change how a date is displayed by changing the NLS_DATE_FORMAT parameter.

CREATE CONTEXT my_ctx USING my_pkg; This creates a context that can only be set by routines in the database package my_pkg, e.g.: CREATE PACKAGE my_pkg AS PROCEDURE set_ctx; END my_pkg; CREATE PACKAGE BODY my_pkg AS PROCEDURE set_ctx IS BEGIN DBMS_SESSION.set_context('MY_CTX','...

The RewriteEngine module within Apache is used to dynamically rewrite URLs and paths depending on various expressions provided: <IfModule mod_rewrite.c> RewriteEngine On RewriteBase / RewriteRule ^index\.php$ - [L] RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{REQUEST_FILENAME} !-d ...

set(my_global_string "a string value" CACHE STRING "a description about the string variable") set(my_global_bool TRUE CACHE BOOL "a description on the boolean cache entry") In case a cached variable is already defined in the cache when CMake processes the ...

set(my_variable "the value is a string") By default, a local variable is only defined in the current directory and any subdirectories added through the add_subdirectory command. To extend the scope of a variable there are two possibilities: CACHE it, which will make it globally av...

When it comes to geographic data, R shows to be a powerful tool for data handling, analysis and visualisation. Often, spatial data is avaliable as an XY coordinate data set in tabular form. This example will show how to create a spatial data set from an XY data set. The packages rgdal and sp provi...

rgdal ESRI shape files can easily be imported into R by using the function readOGR() from the rgdal package. library(rgdal) shp <- readORG(dsn = "/path/to/your/file", layer = "filename") It is important to know, that the dsn must not end with / and the layer does not all...

package { import flash.text.TextField; import flash.display.Sprite; public class TextHello extends Sprite { public function TextHello() { var tf:TextField = new TextField(); tf.text = "Hello World!" tf.x = 50; tf...

Concurrent collections are a generalization of thread-safe collections, that allow for a broader usage in a concurrent environment. While thread-safe collections have safe element addition or removal from multiple threads, they do not necessarily have safe iteration in the same context (one may not...

macro(set_my_variable _INPUT) if("${_INPUT}" STREQUAL "Foo") set(my_output_variable "foo") else() set(my_output_variable "bar") endif() endmacro(set_my_variable) Use the macro: set_my_variable("Foo") message(STATUS ${my_outpu...

macro(set_custom_variable _OUT_VAR) set(${_OUT_VAR} "Foo") endmacro(set_custom_variable) Use it with set_custom_variable(my_foo) message(STATUS ${my_foo}) which will print -- Foo