Wednesday, May 30, 2018

Error in rJava::.jcall(driver@jdrv, "Ljava/sql/Connection;", "connect", : java.sql.SQLException: Network error IOException: Connection refused: connect

Error in rJava::.jcall(driver@jdrv, "Ljava/sql/Connection;", "connect", :

java.sql.SQLException: Network error IOException: Connection refused: connect

Why do I get java.sql.SQLException: "Network error IOException: Connection refused: connect" when trying to get a connection?

The "Connection refused" exception is thrown by jTDS when it is unable to connect to the server. There may be a number of reasons why this could happen:
The server name is misspelled or the port number is incorrect.
SQL Server is not configured to use TCP/IP. Either enable TCP/IP from SQL Server's Network Utility app or have jTDS connect via named pipes (see the URL format for information on how to do this).
There is a firewall blocking port 1433 on the server.

To check whether TCP/IP is enabled and the port is not blocked you can use "telnet <server_host> 1433". Until telnet doesn't connect, jTDS won't either. If you can't figure out why, ask your network administrator for help.

Friday, September 08, 2017

Wake up and Learn Big Data

Wake up and Learn BIG DATA:

I am going to start a tutorial series on big data for the SQL developers. This is the time you should learn big data and start improving your skills parallel to survive in current market scenario.

In this tutorial, I will be guide you through apache Hadoop installation, development and other big data technologies.

In current scenario, the companies are considering new technologies for their new solutions which will create new jobs so you need to consider these learnings for you profile improvement.

Course content:

1. What is big data:

2. Why Big Data is required.

3. Different big data technologies.

4. Back ground of apache Hadoop.

5. Prerequisite for installing Apache Hadoop.

6. Installing ubuntu with dual boot system.

7. Understanding basis architecture of Apache Hadoop.

8. Setting up machine for Hadoop.

9. Hadoop single node cluster installation.

Thursday, June 01, 2017

What are the types of database schema in data warehouse ?

Star Schema:

A star schema is the one in which a central fact table is sourrounded by denormalized dimensional tables. A star schema can be simple or complex. A simple star schema consists of one fact table where as a complex star schema have more than one fact table.

Snow Flake Schema:

A snow flake schema is an enhancement of star schema by adding additional dimensions. Snow flake schema are useful when there are low cardinality attributes in the dimensions.

Galaxy Schema:

Galaxy schema contains many fact tables with some common dimensions (conformed dimensions). This schema is a combination of many data marts.

Fact Constellation Schema:

The dimensions in this schema are segregated into independent dimensions based on the levels of hierarchy. For example, if geography has five levels of hierarchy like teritary, region, country, state and city; constellation schema would have five dimensions instead of one.

Monday, August 15, 2016

What are the limitations in SSRS on SQL Server express edition?

Microsoft offers reporting services free as part of SQL Server Express with Advance Services edition. But it has the following limitations:

  • Management Studio cannot be used to administer report server

  • Report Models will not be available

  • Report Builder is not available

  • Caching, History and Delivery of Report is not available.

  • SQL Server agent is not available

  • No scheduling is possible

  • Remote server database is not available for Report Data Source (Local SQL Server is a only option,)

  • We cannot store the report server database on a remote server (it has to be local only)

  • Reports can be rendered only in Excel, PDF, Image formats only

  • Reporting Services will not be able to use more than 1 GB of RAM

  • No Subscriptions (Standard and Data Driven) can be made

  • Can not be integrated with Share Point

  • Can not implement Role based security

  • Only named instances is supported

Scale-out Report Servers will not be available