Introduction of dcl in sql -: The full name of the dcl is Data Control Language. A data control language (dcl) is a syntax similar to a computer programming language used to control access to data stored in a database. In particular, it is a component of Structured Query Language (SQL). In other words we can… Read More »
Internet Databases Introduction-: The expansion of internet and intranet enabled the user to access a large number of data sources available. One of major achievements of this expansion is E commerce which include purchasing of items ranging from a small pens,books,to all other types of consumer goods through internet. Various site are available which provide… Read More »
Index In sql :- An index is a schema object that can speed up the retrieval of rows by using a pointer. Indexes can be created explicitly or automatically. If we do mot have an index on the column, then a full table scan will occur. An index provides direct and fast access to rows in… Read More »
Sequence in sql-: A sequence is a database object created by a user, and can be shared by multiple users to generate unique integers. We can use the sequence to automatically generate unique integers. A typical usage for sequences is to create a primary key value, which must be unique for each row. The sequence is… Read More »
Views in sql:- We can present logical subsets or combination of data by creating views of tables. A view is a logical table based on a table or another view. A view contains no data of its own but is like a window through which data from tables can be viewed or changed. The tables… Read More »
Constraints in sql-: An integrity constraint can be thought of as a way to define a business rule for a column or a table. Integrity constraints are defined with a table and are stored as part of the table’s definition in the data dictionary. This is advantageous as if a rule changes then it has… Read More »
Data Definition Language (DDL)- In the previous post we read that the DDL is the part of SQL. It is the statement of sql . DDL is a standard for commands that define the different structures in a database. DDL statements create, modify, and remove database objects such as tables, indexes, and users. Common DDL statements… Read More »
Subquery in sql-: Suppose we want ti write a query to find out who earns a salary more then Rames’s salary. To solve this problem we need two query first find out the Ramesh salary and second who earn more then Ramesh. we can solve this problem by combine two query placing one query inside… Read More »
SQL Joins -: Display data from multiple tables in sql called the joins. In other words we can say when data from more then one table in database is required a join condition is use there. In one table row is Joined to another table row according to common value existing in corresponding column. as… Read More »
Limiting rows using a selection in sql -: We can restrict the row returned the query by using the where clause as like this Select [Distinct] {* ! column [alias], ….} from table {where condition(S)]; In this syntax : Where – The where clause can compare value in column literal value arithmetic expression or function. It… Read More »