what is data reader object

A Data reader is an object that is used to read data from the data sources. This can only perform read operation and not update operation on the data source. The data is retrieved as a data stream from the data source.

Full Answer

What is DataReader object in Java?

As we will remember DataReader object provides a read only, forward only, high performance mechanism to retrieve data from a data store as a data stream, while staying connected with the data source. The DataReader is restricted but highly optimized.

What is the use of DataReader in Ado?

DataReader In C#. The DataReader object is used for accessing data from the data store and is one of the two mechanisms that ADO.NET provides.

What is a DataReader in web development?

Techopedia explains DataReader. The .NET Framework includes a suite of software called ADO.NET. In this general category, the DataReader is designed to parse a Tabular Data Stream from SQL or from a continuous stream of data. Taking an unbuffered stream of data, the DataReader can use a strong or weak typing approach to process that data.

What is the use of oledbdatareader?

An oledbDataReader object is used to connect to OLEDB data sources and fetch data from them. Like SQLDataReader, oledbdata reader should also be open before performing read operation. An oledb data reader is initialized as follows. Where the executereader is used to carry out the SQL statements or procedures.

What does DataReader object do?

The DataReader Object provides a connection oriented data access to the Data Sources. A Connection Object can contain only one DataReader at a time and the connection in the DataReader remains open, also it cannot be used for any other purpose while data is being accessed.

What is DataReader object in C#?

A data reader provides an easy way for the programmer to read data from a database as if it were coming from a stream. The DataReader is the solution for forward streaming data through ADO.NET. The data reader is also called a firehose cursor or forward read-only cursor because it moves forward through the data.

How do you use a DataReader?

To retrieve data using a DataReader, create an instance of the Command object, and then create a DataReader by calling Command. ExecuteReader to retrieve rows from a data source.

What is a DataSet object?

The DataSet object is central to supporting disconnected, distributed data scenarios with ADO.NET. The DataSet is a memory-resident representation of data that provides a consistent relational programming model regardless of the data source.

What is SQL DataReader?

The ADO.NET SqlDataReader class in C# is used to read data from the SQL Server database in the most efficient manner. It reads data in the forward-only direction. It means, once it read a record, it will then read the next record, there is no way to go back and read the previous record.

What is the difference between DataReader and DataSet?

DataReader provides faster performance, but has read-only and forward-only access. DataSet, on the other hand, is high resource-consuming, but offers more control and a disconnected nature.

Can DataReader have multiple tables?

Answers. It IS possible to handle multiple result sets with a reader. string sqlText = "Select this, that from here; select somethingelse from there"; ...

What is DataReader and DataAdapter?

DataAdapter is an intermediate layer/ middleware which acts a bridge between the DataSet and a Database whereas DataReader provides forward-only, read-only access to data using a server-side cursor (simply put it is ued to read the data).

Which function of DataReader is used to get the data from it?

The DataReader provides an unbuffered stream of data that allows procedural logic to efficiently process results from a data source sequentially. The DataReader is a good choice when retrieving large amounts of data because the data is not cached in memory.

How many objects are in a DataSet?

It is one of the most popular and challenging object detection datasets today. It contains about 164,000 images and 897,000 annotated objects from 80 categories.

What is a object called in a database?

A database object in a relational database is a data structure used to either store or reference data. The most common object that people interact with is the table. Other objects are indexes, stored procedures, sequences, views and many more.

What are types of data sets?

In Statistics, we have different types of data sets available for different types of information....They are:Numerical data sets.Bivariate data sets.Multivariate data sets.Categorical data sets.Correlation data sets.

What is DataReader and DataAdapter?

DataAdapter is an intermediate layer/ middleware which acts a bridge between the DataSet and a Database whereas DataReader provides forward-only, read-only access to data using a server-side cursor (simply put it is ued to read the data).

What is the use of SqlDataAdapter in C#?

SqlDataAdapter is used in conjunction with SqlConnection and SqlCommand to increase performance when connecting to a SQL Server database. If you are using SQL Server stored procedures to edit or delete data using a DataAdapter , make sure that you do not use SET NOCOUNT ON in the stored procedure definition.

Which is faster DataReader or DataAdapter?

Answers. Datareaders are fast compare to DataAdapters/DataSets because of the following reason. DataReader offers better performance because it avoids the performance and memory overhead associated with the creation of the DataSet.

What is disconnected data architecture in C#?

Disconnected architecture means, you don't need to connect always when you want to get data from the database. You can get data from dataset; basically DataSet is a collection of datatables. We can store the database table, view data in the DataSet and can also store the xml value in dataset and get it if required.

What is a datareader in ASP?

DataReaders provide a very efficient way to access data, and can be thought of as a Firehose cursor from ASP Classic, except that no server-side cursor is used. A DataReader parses a Tabular Data Stream from Microsoft SQL Server, and other methods of retrieving data from other sources.

Why are datareaders so good?

DataReaders have a small footprint and good performance because each is tailor-made to the task at hand, however this makes it more difficult to write an application that can be moved from one backend data source to another. Some provider-specific DataReaders expose types used by the underlying database - for example, int values can be null in Microsoft SQL Server, but not in the .NET Framework prior to version 2.0.

What is weakly typed data retrieval?

Weakly typed data retrieval allows for quick code writing, and allows for the data to be used in some fashion when the developer doesn't know beforehand what types will be returned. Further, with some effort, the programmer can extract the value into a variable of the proper type by using the GetFieldType or GetDataTypeName methods of the DataReader.

Can a datareader be used in place of a data table?

A DataReader can only be used against an (already) open database connection; that connection isn't closed until the DataReader's Dispose method is called. If an exception is thrown while the data is being processed, for example as described in Strong and weak typing, above, the Dispose method will never be called if the developer writes code explicitly declaring and disposing the DataReader without the use of a try - finally block. The C# using construct is a good way to avoid this problem, as shown below in the code example.

What is a data reader in C#?

C# DataReader class represents a data reader. The DataReader provides a read-only, forward-only mechanism to access data via ADO.NET from a datasource.

What are the two objects that ADO.NET uses to read data?

There are two common objects in ADO.NET to read data, DataSet and DataReader. C# DataSet and C# DataReader classes represent these objects. In this article, we'll learn about ADO.NET DataReader and how to use a DataReader in C#.

What is the ExecuteReader method?

As you've seen in the previous examples, you call the ExecuteReader method of the Command object, which returns an instance of the DataReader. For example, use the following line of code:

What is a data reader?

A Data reader is an object that is used to read data from the data sources. This can only perform read operation and not update operation on the data source. The data is retrieved as a data stream from the data source. Though the data reader is restricted in terms of only reading operation, it is highly effective and optimized as it is read only and forward only. There are two types of providers in the .Net Framework, they are SQLDataReader and OleDbDataReader. The data reader increases the application performance by reducing system overhead as it stores the only row in memory at a given point of time. This article will cover in detail the data reader in c# along with appropriate examples.

How does a data reader work?

The data reader object has a read method that can be used to access rows from the result set. Each column value can be accessed either using their name or using their column order in which they appear on the result set. To improve efficiency, a set of pre-defined type conversion methods to access values as such. Data reader is advised to use when working large sets of data as the data is not stored in cache memory. It is always advisable to close the data reader object once it is used. If the command has some return values or output parameters, it is only available once the data reader is closed. Another important thing to keep in mind while using data reader is that when a connection is used by a data reader another data reader or any other operation can’t be performed on that connection. Also, one important thing to remember is only forward accessing the dataset is possible. We can iterate to the next record only and not to the previous one.

What is the read method of data reader?

Before reading from any data reader, it should always be open and should point to the first record. The read () method of data reader is used to read and it moves forward to the next row. The oledb data reader also behaves in the same way. It is available in the name space System.Data.OleDb and the corresponding assembly is System.Data.OleDb.dll.

Where is SQL Data Reader?

The sql data reader is available in the namespace System.Data.SqlClient and the corresponding assembly is System.Data.SqlClient.dll. A SQL data reader is initialized as follows.

When is a data reader only available?

If the command has some return values or output parameters, it is only available once the data reader is closed . Another important thing to keep in mind while using data reader is that when a connection is used by a data reader another data reader or any other operation can’t be performed on that connection.

Is a data reader read only?

Though the data reader is restricted in terms of only reading operation, it is highly effective and optimized as it is read only and forward only. There are two types of providers in the .Net Framework, they are SQLDataReader and OleDbDataReader.

Why is the DataReader important?

The DataReader is a good choice when retrieving large amounts of data because the data is not cached in memory. You should always call the Close method when you have finished using the DataReader object. If your Command contains output parameters or return values, they will not be available until the DataReader is closed.

Why use ADO.NET DataReader?

You can use the ADO.NET DataReader to retrieve a read-only, forward-only stream of data from a database. Using the DataReader can increase application performance and reduce system overhead because only one row at a time is ever in memory.

What is a DataReader implementation?

The DataReader implementation must provide two basic capabilities: forward-only access over one or more of the resultsets obtained by executing a Command, and access to the column values within each row. Data types from your data source will be stored in your .NET-based application as .NET Framework types. Your DataReader implementation will also provide strongly typed accessor methods for your DataReader that return column values as .NET Framework types. Examples of a strongly typed accessor would be GetInt32, GetString, and so on.

Can a.NET data provider expose proprietary types?

If your .NET data provider has proprietary types that cannot adequately be exposed as .NET Framework types, you may extend the interfaces to support proprietary types, then add typed accessors for your DataReader that return proprietary types as well. For example, you can add GetMyStructure, GetMyTimeStamp, and so on. An example of this is the SQL Server .NET Data Provider, which exposes proprietary types using the System.Data.SqlTypes Namespace. The SqlDataReader then exposes those types as SqlTypes using strongly typed accessor methods. For example: GetSqlBinary, GetSqlDateTime, GetSqlDecimal, and so on.

Can you use a datareader while it is open?

Note that while a DataReader is open, the Connection is in use exclusively by that DataReader. You will not be able to execute any commands for the Connection, including creating another DataReader, until the original DataReader is closed.

How does ADO.NET DataReader work?

You can use the ADO.NET DataReader to retrieve a read-only, forward-only stream of data from a database. Results are returned as the query executes, and are stored in the network buffer on the client until you request them using the Read method of the DataRea der. Using the DataReader can increase application performance both by retrieving data as soon as it is available, and (by default) storing only one row at a time in memory, reducing system overhead.

What is a data adapter?

A DataAdapter is used to retrieve data from a data source and populate tables within a DataSet. The DataAdapter also resolves changes made to the DataSet back to the data source. The DataAdapter uses the Connection object of the .NET Framework data provider to connect to a data source, and it uses Command objects to retrieve data from and resolve changes to the data source.

What is a data reader?

2. Data reader is an object through which you can read a sequential stream of data. it's a forward only data wherein you cannot go back to read previous data. data set and data adapter object help us to work in disconnected mode. data set is an in cache memory representation of tables. the data is filled from the data source to ...

What is the difference between a data adapter and a data reader?

DataAdapter follows connectionless-oriented architecture which simply means you need not necessarily be connected to a data-source whereas DataReader is a connection-oriented architecture which means it needs an active connection to a data-source for it to operate.

What is ADO.NET?

ADO.NET provides two central Data Access Components. The excellent thing is that, they are common across all Databases, be it SQL Server or other competitive databases. Its only the namespace to be used, that differs, while using a Database other than SQL Server.

Is DataReader faster than DataAdapter?

DataAdapter is comparatively slower whereas using DataReader can increase application performance both by retrieving data as soon as it is available, and (by default) storing only one row at a time in memory, reducing system overhead.

Can a DataReader read data from a Database?

Using DataSet we can manipulate and update a DataSet's contents while disconnected from the Datasource and send any modified data back for processing using a related DataAdapter whereas DataReader can only read data from a Database & cannot modify it.

What is Pandas Datareader in Python?

Pandas Datareader is a Python package that allows us to create a pandas DataFrame by using some popular data sources available on the internet including:

Working with Pandas Datareader using Python

I hope you now have understood what is pandas_datareader, now let’s see how to use this package to read the stock price data from yahoo finance using Python. If you have never used it before then you can easily install it by using the pip command; pip install pandas_datareader.

Summary

So this is how easy it is to read and store the stock price data into a pandas DataFrame. In this article, I collected the stock price data of Tesla from Yahoo Finance. I hope you liked this article on a tutorial on pandas_datareader using Python. Feel free to ask your valuable questions in the comments section below.

Overview

In ADO.NET, a DataReader is a broad category of objects used to sequentially read data from a data source. DataReaders provide a very efficient way to access data, and can be thought of as a Firehose cursor from ASP Classic, except that no server-side cursor is used. A DataReader parses a Tabular Data Stream from Microsoft SQL Server, and other methods of retrieving data from other sources.

DataReader types

Strong vs weak typing

Common errors

Sample code