Tutorial by Examples: l

An example cannot be associated with a version number directly. Parts of it can however be declared to apply only for certain versions. <!-- if version [eq Java SE 1.3] --> This content is for Java SE 1.3 <!-- end version if -->

If there are many version tables, the title of the desired one has to be included in angle brackets. <!-- if version <Micro Framework> [eq 4.4] --> This content is for Micro Framework 4.4 <!-- end version if -->

The markdown help states Available conditionals are gt, gte, lt, lte, eq, and neq. <!-- if version [eq C++03] --> eq equal to <!-- end version if --> <!-- if version [neq C++03] --> neq not equal to <!-- end version if --> <!-- if version [gt C++03] -...

Multiple conditions can be used. <!-- if version [lte 1.2.0] [gt 1.3.12] [gt 1.4.9] [neq 1.2.0] [eq 1.5.7] --> content <!-- end version if -->

POSIX thread library provides implementation of the mutex primitive, used for the mutual exclusion. Mutex is created using pthread_mutex_init, and destroyed using pthread_mutex_destroy. Obtaining a mutex can be done using pthread_mutex_lock or pthread_mutex_trylock, (depending if the timeout is desi...

The command :g/apples/y A will yank all lines containing the word apples into the a register, which can be pasted with "ap. Any regular expression can be used. Note the space before the A, and the capitalization of the register letter. If a capital letter is used as the yank register, matc...

@parallel can be used to parallellize a loop, dividing steps of the loop up over different workers. As a very simple example: addprocs(3) a = collect(1:10) for idx = 1:10 println(a[idx]) end For a slightly more complex example, consider: @time begin @sync begin @paral...

The Julia documentation advises that pmap() is designed for the case where each function call does a large amount of work. In contrast, @parallel for can handle situations where each iteration is tiny, perhaps merely summing two numbers. There are several reasons for this. First, pmap incurs ...

SELECT s.name AS [schema], t.object_id AS [table_object_id], t.name AS [table_name], c.column_id, c.name AS [column_name], i.name AS [index_name], i.type_desc AS [index_type] FROM sys.schemas AS s INNER JOIN sys.tables AS t ON s.schema_id = t.schema_id I...

Whenever you change data, in a Data Manipulation Language(DML) command, you can wrap your changes in a transaction. DML includes UPDATE, TRUNCATE, INSERT and DELETE. One of the ways that you can make sure that you're changing the right data would be to use a transaction. DML changes will take a loc...

One might want to GROUP BY more than one column declare @temp table(age int, name varchar(15)) insert into @temp select 18, 'matt' union all select 21, 'matt' union all select 21, 'matt' union all select 18, 'luke' union all select 18, 'luke' union all select 21, 'luke' union all select 1...

-- Identity primary key - unique arbitrary increment number create table person ( id int identity(1,1) primary key not null, firstName varchar(100) not null, lastName varchar(100) not null, dob DateTime not null, ssn varchar(9) not null )

-- GUID primary key - arbitrary unique value for table create table person ( id uniqueIdentifier default (newId()) primary key, firstName varchar(100) not null, lastName varchar(100) not null, dob DateTime not null, ssn varchar(9) not null )

-- natural primary key - using an existing piece of data within the table that uniquely identifies the record create table person ( firstName varchar(100) not null, lastName varchar(100) not null, dob DateTime not null, ssn varchar(9) primary key not null )

-- composite key - using two or more existing columns within a table to create a primary key create table person ( firstName varchar(100) not null, lastName varchar(100) not null, dob DateTime not null, ssn varchar(9) not null, primary key (firstName, lastName, dob) )

ALTER TABLE person ADD CONSTRAINT pk_PersonSSN PRIMARY KEY (ssn) Note, if the primary key column (in this case ssn) has more than one row with the same candidate key, the above statement will fail, as primary key values must be unique.

ALTER TABLE Person DROP CONSTRAINT pk_PersonSSN

You can use limit to tell the number of records to be fetched, and use offset to tell the number of records to skip before starting to return the records. For Example User.limit(3) #returns first three records It will generate following sql query. "SELECT `users`.* FROM `users` LIMIT 3&q...

In the absence of explicit initialization, external and static variables are guaranteed to be initialized to zero; automatic variables (including register variables) have indeterminate1 (i.e., garbage) initial values. Scalar variables may be initialized when they are defined by following the name w...

AppDomain.UnhandledException This event provides notification of uncaught exceptions.It allows the application to log information about the exception before the system default handler reports the exception to the user and terminates the application.If sufficient information about the state of the a...