Data Dictionary
What is Data dictionary ? Data Dictionary is basically a repository which contains data about the database such as information about tables , column names,their length , datatypes, attributes and other database structures etc....
Category: SQL
Internal Working of Query Execution
When we execute an SQL statement e.g. SELECT * FROM EMP , Lets see what happens behind the scene i.e Internal working of query execution.In other words , Life cycle of an SQL statement...
Types of Constraints
In the Previous post we studied about ‘ What are Constraints ? ‘. Now we will read about different Types of Constraints. What are the Different Types of Constraints : 1. NOT NULL Constraint...
Constraints in SQL
What are Constraints ?? Constraints may be defined as rules or conditions applied on the data columns of the table, that restrict the type of data entering into the table.They act as filter between...
Data Control Language in SQL ( DCL Commands )
What are DCL Commands ?? Data Control Language or shortly called DCL commands are a set of SQL Commands that provides database security by granting or removing various permissions or privileges for the...
Distinct Clause in SQL
Distinct Clause in SQL is used to fetch only unique values and remove the duplicate values from the result. Key – Points : The changes made by Distinct Clause are not permanent and are...
Backup Table in SQL
Backup Table in SQL, as the name suggests, is the copy of an existing table whose backup we need to take . Constraints on the original table are not copied in the Backup table...
Order By Clause in SQL
Order By Clause in SQL is used to sort the resultset in ascending or descending order. Key – Points : By default it sorts the result in Ascending order. Asc Keyword is used for...
Logical Operators
In this post , we will discuss about Logical Operators. AND Operator : AND Operator is used to filter the records based on two or more than two conditions. It is specified in the WHERE...
Deadlocks in SQL
For a transactional database , Deadlocks in SQL may be defined as a situation in which two or more oracle sessions are competing against the same data and waiting for each other to release...