What Is a Data Set?

A data set, also known as a data set, data set, or data set, is a collection of data.

A data set (or dataset) is a collection of data, usually in tabular form. Each column represents a specific variable. Each row corresponds to a problem with a member's data set. It lists the values for each variable, such as the height and weight of an object or a random number of values. Each value is called a data sheet. Corresponding to the number of rows, the data of this dataset may include one or more members. ^[1]

Chinese name: data set
Foreign name: Data set

Alias: Data set
Definition: A collection of data

Data set principles and classification

Historically, the term originated in the mainframe field, where it had a well-defined meaning, very close to modern computer archives. This topic is not included here.

In the simplest case, there is only one variable, and then the data set consists of a list of values, often described as a list. Despite the name, such a single data set is not a common set of mathematical meanings because a given value may appear multiple times. The usual order is not important, and then a collection of such values may be treated as a multiple set rather than a (sequential) list.

The value may be a number, such as a real number or an integer, such as how many centimeters a person is, but it may also be symbolic data (that is, not including numbers), such as a person's race. More generally, value can be any type described as a measure of some degree. For each variable, usually all values are homogeneous. But it could also be "missing values", some of which need to be pointed out.

Data sets can be divided into typed data sets and untyped data sets.

Typed dataset: This dataset is derived from the base DataSet class, and then uses the information in the XML schema file (.xsd file) to generate a new class. The information in the schema (tables, columns, etc.) is generated as a set of first-class objects and attributes and compiled into this new dataset class. Tables and columns can be referenced directly by name, and the type of elements can be intelligently sensed in VS.NET.

Untyped dataset: This dataset does not have a corresponding built-in architecture. Like typed datasets, untyped datasets also contain tables, columns, and so on, but they are only exposed as collections. Columns need to be referenced through the Tables collection.

Data set role

Data set statistics

The statistical data set usually comes from the sampled statistical population obtained from actual observations, and each row corresponds to a component of the observations, the population. The dataset may further generate algorithms for certain kinds of software for testing purposes. Some modern statistical analysis software, such as PSPP, still exists in the classic dataset way. Common demographic and human resource statistics datasets include: ^[2] Gravesite locations of Veterans and beneficiaries in ALASKA, as of January 2011. (Alaska Veterans Cemetery Locations and Beneficiaries, since January 2011), 2007-2008 County-to-County Migration Outflow (2007-2008).

Dataset database

Data sets store data in disconnected caches. The structure of a data set is similar to that of a relational database; it exposes a hierarchical object model of tables, rows, and columns. In addition, it contains constraints and relationships defined for the data set.

Delphi 4 Dataset Delphi 4

There are four types of standard data set components in Delphi 4, which are TTable, TQuery, TStoredProc, and TClientDataSet. These data set components are inherited from a common base class TDataSet, of which only TClientDataSet is directly inherited from TDataSet, and the direct superior of TTable, TQuery, TStoredProc is TDBDataSet, the superior of TDBDataSet is TBDEDataSet, the superior of TBDEDataSet It is TDataSet. The inheritance relationship between these classes can be represented by Figure 6.1.

TDataSet is an abstract base class for all data sets. Most of its properties and methods are virtual or abstract. The so-called virtual methods means that these methods can be overloaded by derived classes. The so-called abstract method means that these methods are only declared and not defined. Derived classes must be given a definition before they can be called. Different derived classes can have different definitions.

Because TDataSet contains abstract methods, you cannot directly create an instance of it, otherwise it will cause runtime errors.

If divided from functions, the properties and methods of TDataSet can be divided into such large blocks: open and close data sets, browse records, edit data, bookmark management, control connections, access fields, record buffer management, filtering, and events. ^[1]

Data Set Tips

Filtering and sorting within a dataset

After populating a data set, you often find it useful to use different subsets of records in the table or to view the data in a different order. You can do this by filtering and sorting the data within the dataset. To simplify this process, you can create a data view that provides objects that can combine filters and sort criteria and can be used as a source for data binding.

Use the built-in data set capabilities to filter and sort instead. There are two options:

(1) The data table supports the Select method, which you can call to filter and sort. This method does not change the content and order of the records in the table; instead, it provides you with a list (or array) of records that represents the conditions you specify.

(2) You can use a data view (DataView object). A data view is an object that acts as a layer above a data table and provides a filtered and sorted view of the table's content. (You can also use the Data View Manager, which behaves like a collection of data views.) A data view is similar to a view in a database because it is not a copy of the data. Instead, it is just another way to look at the data in the table.

Dataset Data View

A data view is an independent object located on a data table. It is a filtered and sorted view of a single piece of data. It can be used as a data source for bound controls, or you can create multiple data views for a data table. The DataRowView object that references the data row, and the RowFilter property of the data view, can be used to filter the records in the data table so that only the records that you want to operate are available. This is useful when working with different subsets of records in a dataset table. To specify filter conditions, you can use the same expression syntax as the syntax used to create a column expression.