In this article, we will learn how to create a RAID 5 Array configuration using the ‘mdadm’ utility.The ‘mdadm’ is a utility which is used to create and manage storage arrays on Linux with RAID capability where the administrators are having great flexibility in managing the individual storages devices and creating the logical storage with a high performance and redundancy.RAID 5 Array is a type where we implement by striping the data across the total available devices. Every component of the each stripe is calculated by parity block. If any device fails the parity block, it will use the remaining ... Read More

In this article, we will learn how to create a RAID 0 Array configuration using the ‘mdadm’ utility.The ‘mdadm’ is a utility which is used to create and manage storage arrays on Linux with RAID capability where the administrators are having a great flexibility in managing the individual storage devices and creating the logical storage with a high performance and redundancy.RAID 0 array will work by dividing the data into small chunks and strips that data across the available storage disks, which means that each and every storage disk will contain a portion of data and when retrieving the data ... Read More

Stored procedures are a pieces of the code in written in PL/SQL to do some specific task. Stored procedures can be invoked explicitly by the user. It's like a java program , it can take some input as a parameter then can do some processing and can return values.On the other hand,  trigger is a stored procedure that runs automatically when various events happen (eg update, insert, delete). Triggers are more like an event handler they run at the specific event. Trigger can not take input and they can’t return values.Sr. No.KeyTriggersStored procedures1Basic trigger is a stored procedure that runs automatically when ... Read More

SQL query is used to fetch data from the database. In some of the scenario you may need some perquisite data to call subsequent SQL query to fetch data from a table so instead of writing two seperate query we can write SQL query within the query.Therefore subQuery is a way to combine or join them in single query. Subqurey can have two types −Correlated subquery - In correlated subquery, inner query is dependent on the outer query. Outer query needs to be executed before inner queryNon-Correlated subquery - In non-correlated query inner query does not dependent on the outer query. ... Read More

Oracle golden gate and oracle active data guard is the data replication technologies. They both are used for data replication but with different strategy. As per the oracle docs −Oracle Active Data Guard provides the best data protection and availability for Oracle Database in the simplest most economical manner by maintaining an exact physical replica of the production copy at a remote location that is open read-only while replication is active. GoldenGate is an advanced logical replication product that supports multi-master replication, hub and spoke deployment and data transformation, providing customers very flexible options to address the complete range of replication requirements. ... Read More

Logical standby and physical standby database in two different types of standby database. In case of any failure of primary database Oracle transfer data from primary database to the standby database. This approach helps us to recover data from standby database in case of any failure.Logical standby database is not the exact copy of the primary database. Logical standby uses LogMiner techniques to transform the archived redo logs into native DML statements (insert, update, delete).  This DML is transported and applied to the standby database.Primary standby database is the exact copy of primary database so it helps to minimize the ... Read More

In Hierarchical data model, relationship between table and data is defined in parent child structure. In this structure data are arranged in the form of a tree structure. This model supports one-to-one and one-to-many relationships.On the other hand, network model arrange data in graph structure. In this model each parents can have multiple children and children can also have multiple parents. This model supports many to many relationships also.Sr. No.KeyHierarchical Data ModelNetwork Data Model1Basic Relationship between records is of the parent child typeRelationship between records is expressed in the form of pointers or links.2        Data Inconsistency It can have data ... Read More

In Relational database tables are associated with each other and we used foreign key to maintain relationships between tables. We used join clause to retrieve data from associated tables. The join condition indicates how column in each table are matched against each other. There are two types of joins clause in SQL Inner join Outer joinOuter join is again divided into parts −LEFT OUTER JOIN - It will return all data of the left table and matched  records in both table RIGHT OUTER JOIN - it will return all the data of the right table and matched records in both tableSr. No.KeyInner joinOuter join1Basic It ... Read More

Both the TRUNCATE statement and the DELETE statement are included in the category of SQL queries for deleting the data stored in a table. They carry out deletion operations on records or rows of a table that are no longer needed. A condition is applied before each entry in the table that is being deleted when using the DELETE command. To put it another way, it is possible to delete one or more rows all at once. However, with the TRUNCATE command, each row is removed from the table simultaneously. When we delete something using the DELETE query, a log ... Read More

An Index is a lookup table associated with an actual table or View that is used by the database to improve the data retrieval performance timing. In an index,  keys are stored in a structure (B-tree) that enables SQL Server to find the rows associated with the key values quickly and efficiently. Index gets created automatically if the primary key and unique key constraints are defined on the table. There are two types of index namely, Clustered Index and Non-Clustered Index. Read this article to learn more about clustered index and non-clustered index and how they are different from each ... Read More