Tutorial by Topics: data

A data.table is an enhanced version of the data.frame class from base R. As such, its class() attribute is the vector "data.table" "data.frame" and functions that work on a data.frame will also work with a data.table. There are many ways to create, load or coerce to a data.tabl...

The special symbol .SD is available in j of DT[i,j,by], capturing the Subset of Data for each by group surviving the filter, i. .SDcols is a helper. Type ?`special-symbols` for the official docs. A reminder: DT[where, select|update|do, by] syntax is used to work with columns of a data.table. T...

Categoricals are a pandas data type, which correspond to categorical variables in statistics: a variable, which can take on only a limited, and usually fixed, number of possible values (categories; levels in R). Examples are gender, social class, blood types, country affiliations, observation time...

Possible Exceptions System.ArrayTypeMismatchException: Attempted to access an element as a type incompatible with the array. This exception can occur when attempting to bind a collection to a non-bindable property when XAML pre-compilation is enabled. A common example is attempting to bind ...

Shows how a sqoop script could be used to import data from various datastores/databases.

MSSQL Syntax: DROP DATABASE [ IF EXISTS ] { database_name | database_snapshot_name } [ ,...n ] [;] MySQL Syntax: DROP {DATABASE | SCHEMA} [IF EXISTS] db_name DROP DATABASE is used for dropping a database from SQL. Be sure to create a backup of your database before dropping it to prevent ...

This FireDAC example, and the others I'm planning to submit, will avoid the use of native calls to asynchronously open the dataset.

Entity Framework Code-First provides a set of DataAnnotation attributes, which you can apply to your domain classes and properties. DataAnnotation attributes override default Code-First conventions. System.ComponentModel.DataAnnotations includes attributes that impacts on nullability or siz...

Python can handle many different types of databases. For each of these types a different API exists. So encourage similarity between those different API's, PEP 249 has been introduced. This API has been defined to encourage similarity between the Python modules that are used to access database...

The most tricky part is finding description for error codes. This site has a most complete list of codes I've found so far. Below you can find a copy cleaned of "@@@"s. Error NumberError Description3Return without GoSub5Invalid procedure call or argument6Overflow7Out of memory9Subscri...

This section provides an overview of what spring-data-jpa is, and why a developer might want to use it. It should also mention any large subjects within spring-data-jpa, and link out to the related topics. Since the Documentation for spring-data-jpa is new, you may need to create initial version...