Tutorial by Examples: u

Use BETWEEN to Filter Results

The following examples use the Item Sales and Customers sample databases. Note: The BETWEEN operator is inclusive. Using the BETWEEN operator with Numbers: SELECT * From ItemSales WHERE Quantity BETWEEN 10 AND 17 This query will return all ItemSales records that have a quantity that is gr...

SQL • Filter results using WHERE and HAVING

UPDATE with data from another table

The examples below fill in a PhoneNumber for any Employee who is also a Customer and currently does not have a phone number set in the Employees Table. (These examples use the Employees and Customers tables from the Example Databases.) Standard SQL Update using a correlated subquery: UPDATE ...

SQL • UPDATE

Setup with sample scollector.toml file

Scollector binaries for Windows, Mac, and Linux are available from the Bosun release page and can be saved to /opt/scollector/ or C:\Program Files\scollector\. The Scollector configuration file uses TOML v0.2.0 to specify various settings and defaults to being named scollector.toml in the same folde...

Bosun • Scollector: Overview

Running Scollector as a service

On Windows you can install Scollector as a service using the -winsvc="install" flag. On Mac and Linux you must manually create a service or init script. For example here is a basic systemd unit file: #Scollector unit file saved to /etc/systemd/system/scollector.service [Unit] Descriptio...

Bosun • Scollector: Overview

Hadoop HDFS disk usage written in Bash

This is a continuous collector that uses the hadoop fs -du -s /hbase/* command to get details about the HDFS disk usage. This metric is very useful for tracking space in an OpenTSDB system. #!/bin/bash while true; do while read -r bytes raw_bytes path; do echo "hdfs.du $(date +&...

Bosun • Scollector: External Collectors

Linux process and systemd service monitoring

Scollector will monitor Linux processes specified in the configuration file. [[Process]] Command = "/opt/bosun/bosun" Name = "bosun" [[Process]] Command = "ruby" Name = "puppet-agent" Args = "puppet" [[Process]] Command = &qu...

Bosun • Scollector: Process and Service Monitoring

Option Groups

You can neatly group your options within a selection menu in order to provide a more structured layout in a long list of options by using the <optgroup> element. The syntax is very basic, by simply using the element with a label attribute to identify the title for the group, and containing ze...

HTML • Selection Menu Controls

Output Element Using For and Form Attributes

The following demo features an <output> element's use of the [for] and [form] attributes. Keep in mind, <output> needs JavaScript in order to function. Inline JavaScript is commonly used in forms as this example demonstrates. Although the <input> elements are type="number&quot...

HTML • Output Element

Output Element with Attributes

HTML • Output Element

NSLog Output Format

NSLog(@"NSLog message"); The message that gets printed by calling NSLog has the following format when viewed in Console.app: DateTimeProgram nameProcess IDThread IDMessage2016-07-1608:58:04.681test[46259:1244773]NSLog message

Objective-C Language • Logging

Accessing overridden default methods from implementing class

In classes, super.foo() will look in superclasses only. If you want to call a default implementation from a superinterface, you need to qualify super with the interface name: Fooable.super.foo(). public interface Fooable { default int foo() {return 3;} } public class A extends Object impl...

Java Language • Default Methods

Restore file to a previous version

To restore a file to a previous version you can use reset. git reset <sha1-of-commit> <file-name> If you have already made local changes to the file (that you do not require!) you can also use the --hard option

Git • Recovering

Specifying structure using XPath expressions

SELECT 'XPath example' AS 'head/title', 'This example demonstrates ' AS 'body/p', 'https://www.w3.org/TR/xpath/' AS 'body/p/a/@href', 'XPath expressions' AS 'body/p/a' FOR XML PATH('html') <html> <head> <title>XPath example</title> &...

Microsoft SQL Server • FOR XML PATH

Padding the output

String can be formatted to accept a padding parameter that will specify how many character positions the inserted string will use : ${value, padding} NOTE: Positive padding values indicate left padding and negative padding values indicate right padding. Left Padding A left padding of 5 (a...

C# Language • String Interpolation

Reducing values

5.1 The reduce() method applies a function against an accumulator and each value of the array (from left-to-right) to reduce it to a single value. Array Sum This method can be used to condense all values of an array into a single value: [1, 2, 3, 4].reduce(function(a, b) { return a + b; }); ...

JavaScript • Arrays

Logical connective of values

5.1 .some and .every allow a logical connective of Array values. While .some combines the return values with OR, .every combines them with AND. Examples for .some [false, false].some(function(value) { return value; }); // Result: false [false, true].some(function(value) { return value...

JavaScript • Arrays

Class lambdas and capture of this

A lambda expression evaluated in a class' member function is implicitly a friend of that class: class Foo { private: int i; public: Foo(int val) : i(val) {} // definition of a member function void Test() { auto lamb = [](Foo &foo, int val) ...

C++ • Lambdas

Simulating variable-length lookbehind with \K

Some regex flavors (Perl, PCRE, Oniguruma, Boost) only support fixed-length lookbehinds, but offer the \K feature, which can be used to simulate variable-length lookbehind at the start of a pattern. Upon encountering a \K, the matched text up to this point is discarded, and only the text matching th...

Regular Expressions • Lookahead and Lookbehind

Double quotes for variable and command substitution

Variable substitutions should only be used inside double quotes. calculation='2 * 3' echo "$calculation" # prints 2 * 3 echo $calculation # prints 2, the list of files in the current directory, and 3 echo "$(($calculation))" # prints 6 Outside of doubl...

Bash • Quoting

Quoting literal text

All the examples in this paragraph print the line !"#$&'()*;<=>? @[\]^`{|}~ A backslash quotes the next character, i.e. the next character is interpreted literally. The one exception is a newline: backslash-newline expands to the empty string. echo \!\"\#\$\&\'\*\;\...

Bash • Quoting