Tutorial by Examples: er

Let's say I have this data: Table items idnametag1exampleunique_tag2foosimple42barsimple3bazhello51quuxworld I'd like to get all those lines and know if a tag is used by other lines SELECT id, name, tag, COUNT(*) OVER (PARTITION BY tag) > 1 AS flag FROM items The result will be: idnametag...

You can indent the text inside here documents with tabs, you need to use the <<- redirection operator instead of <<: $ cat <<- EOF This is some content indented with tabs `\t`. You cannot indent with spaces you __have__ to use tabs. Bash will remove empty space befo...

2.05b You can feed a command using here strings like this: $ awk '{print $2}' <<< "hello world - how are you?" world $ awk '{print $1}' <<< "hello how are you > she is fine" hello she You can also feed a while loop with a here string: $ while IFS...

Use putAll to put every member of one map into another. Keys already present in the map will have their corresponding values overwritten. Map<String, Integer> numbers = new HashMap<>(); numbers.put("One", 1) numbers.put("Three", 3) Map<String, Integer> othe...

If you want to get the versioned project's data, but you don't need any of the version control capabilities offered by Subversion, you could run svn export <URL> command. Here is an example: $ svn export https://svn.example.com/svn/MyRepo/MyProject/trunk As a result, you will get the proje...

A wide variety of standard library functions have among their effects copying byte sequences from one memory region to another. Most of these functions have undefined behavior when the source and destination regions overlap. For example, this ... #include <string.h> /* for memcpy() */ ch...

Requirements: OS X 10.8 “Mountain Lion” or newer required to run Docker. While the docker binary can run natively on Mac OS X, to build and host containers you need to run a Linux virtual machine on the box. 1.12.0 Since version 1.12 you don't need to have a separate VM to be installed, as Docker...

Since Groups are "numbered" some engines also support matching what a group has previously matched again. Assuming you wanted to match something where two equals strings of length three are divided by a $ you'd use: (.{3})\$\1 This would match any of the following strings: "abc$...

Evaluates its first operand, and, if the resulting value is not equal to zero, evaluates its second operand. Otherwise, it evaluates its third operand, as shown in the following example: a = b ? c : d; is equivalent to: if (b) a = c; else a = d; This pseudo-code represents it : c...

Evaluates its left operand, discards the resulting value, and then evaluates its rights operand and result yields the value of its rightmost operand. int x = 42, y = 42; printf("%i\n", (x *= 2, y)); /* Outputs "42". */ The comma operator introduces a sequence point between i...

This example shows how to match an input against several values: def f(x: Int): String = x match { case 1 => "One" case 2 => "Two" case _ => "Unknown!" } f(2) // "Two" f(3) // "Unknown!" Live demo Note: _ is the fall th...

In standard pattern matching, the identifier used will shadow any identifier in the enclosing scope. Sometimes it is necessary to match on the enclosing scope's variable. The following example function takes a character and a list of tuples and returns a new list of tuples. If the character existed...

In order to get const char* access to the data of a std::string you can use the string's c_str() member function. Keep in mind that the pointer is only valid as long as the std::string object is within scope and remains unchanged, that means that only const methods may be called on the object. C++1...

Inheritance works just like it does in other object-oriented languages: methods defined on the superclass are accessible in the extending subclass. If the subclass declares its own constructor then it must invoke the parents constructor via super() before it can access this. class SuperClass { ...

This example shows the usage of the ILGenerator by generating code that makes use of already existing and new created members as well as basic Exception handling. The following code emits a DynamicAssembly that contains an equivalent to this c# code: public static class UnixTimeHelper { priva...

Before publishing a package you have to version it. npm supports semantic versioning, this means there are patch, minor and major releases. For example, if your package is at version 1.2.3 to change version you have to: patch release: npm version patch => 1.2.4 minor release: npm version min...

Can be used to shorten if/else operations. This comes in handy for returning a value quickly (i.e. in order to assign it to another variable). For example: var animal = 'kitty'; var result = (animal === 'kitty') ? 'cute' : 'still nice'; In this case, result gets the 'cute' value, because the v...

Generally To use regular expression specific characters (?+| etc.) in their literal meaning they need to be escaped. In common regular expression this is done by a backslash \. However, as it has a special meaning in Java Strings, you have to use a double backslash \\. These two examples will not ...

git cherry-pick <commit-hash> will apply the changes made in an existing commit to another branch, while recording a new commit. Essentially, you can copy commits from branch to branch. Given the following tree (Source) dd2e86 - 946992 - 9143a9 - a6fd86 - 5a6057 [master] \ ...

/* declare items of the enum */ #define FOREACH \ X(item1) \ X(item2) \ X(item3) \ /* end of list */ /* define the enum values */ #define X(id) MyEnum_ ## id, enum MyEnum { FOREACH }; #undef X /* convert an enum value to its identifier */ const char * enum2string(int...