SQL stands for Structured Query Language. A query language is a kind of programming language that's designed to facilitate retrieving specific information from databases, and that's exactly what SQL does.
An operator is a reserved word or a character used primarily in an SQL statement's WHERE clause to perform operation(s), such as comparisons and arithmetic operations.
SQL commands are the instructions used to communicate with a database to perform tasks, functions, and queries with data. SQL commands can be used to search the database and to do other functions like creating tables, adding data to tables, modifying data, and dropping tables
MySQL queries are SQL functions that help us to access a particular set of records from a database table. We can request any information or data from the database using the clauses or let’s say SQL statements.
A query is a question or inquiry to a set of data. We use SQL, or Structured Query Language, to retrieve data from databases. When we build the structure we are pulling data from tables and fields. The fields are columns in the database table while the actual data makes up the rows.
An SQL key is either a single column (or attribute) or a group of columns that can uniquely identify rows (or tuples) in a table. SQL keys ensure that there are no rows with duplicate information.
Joins in SQL can be of four different types, subjected to the outcome expected by combining records from two or more tables by making use of the common columns from tables involved in the Join function. Inner Join is used to get records with same values In both tables, Left Join is used to get all records from Left side table and only matching values from right table and Right Join is used to get all records from Right table and only matching records in left table. finally Full Join to get all the records from both tables irrespective of matching records.
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Views & Stored Procedure in SQL Server
In this article, I am going to describe how to use views in SQL Server 2005 database. A view is a virtual table that consists of columns from one or more tables. Though it is similar to a table, it is stored in the database. It is a query stored as an object. Hence, a view is an object that derives its data from one or more tables. These tables are referred to as base or underlying tables. Once you have defined a view, you can reference it like any other table in a database.
A view serves as a security mechanism. This ensures that users are able to retrieve and modify only the data seen by them. Users cannot see or access the remaining data in the underlying tables. A view also serves as a mechanism to simplify query execution. Complex queries can be stored in the form as a view, and data from the view can be extracted using simple queries.
A view consists of a SELECT statement that stored with a database. Because views are stored as part of the database, they can be managed independently of the applications that use them.
A view behaves like a virtual table. Since you can code a view name anywhere you can code a table name. a view is sometimes called a viewed table.
Views can be used to restrict the data that a user is allowed to access or to present data in a form that is easy for the user to understand. In some database users may be allowed to access data only through views.
In this example, I am using my Vendor database which has these fields.
You can execute your view like this, in this example, VendorData is my View name.
Use Vendor
GO
SELECT * FROM VendorData WHERE VendorState = ‘PA’ORDERBY PostedDate
GO
Output
Figure 2.
Stored Procedure in SQL Server
A stored procedure is a set of one or more SQL statements that are stored together in database. To create a stored procedure use CREATE PROCEDURE statement. To use the stored procedure you send a request for it to be executed. When server receives the request, it executes the stored procedure.
Stored procedures assist in achieving a consistent implementation of logic across applications. The SQL statements and logic needed to perform a commonly performed task can be designed, coded, and tested once in a stored procedure. Each application needing to perform that task can then simply execute the stored procedure. Coding business logic into a single stored procedure also offers a single point of control for ensuring that business rules are correctly enforced.
Stored procedures can also improve performance. Many tasks are implemented as a series of SQL statements. Conditional logic applied to the results of the first SQL statements determines which subsequent SQL statements are executed. If these SQL statements and conditional logic are written into a stored procedure, they become part of a single execution plan on the server. The results do not have to be returned to the client to have the conditional logic applied; all of the work is done on the server.
There are some concepts of stored procedures.
A stored procedure is one or more SQL statements that have been compiled and stored with database. A stored procedure can be started by application code on the client.
Stored procedure can improve database performance because the SQL statements in each procedure are only compiled and optimized the first time they are executed. In contrast SQL statements that are sent from a client to the server have to be compiled and optimized every time they are executed.
In addition to SELECT statement, a stored procedure can contain othe SQL statements such as INSERT, UPDATE, DELETE. It also contains control-of-flow language.
A trigger is a special type of procedure that executes when rows are inserted, updated or deleted from table.
A user defined function(UDF) is a special type of procedure that can return a value or a table.
Example
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
— =============================================
— Author: <Author,,Name>
— Create date: <Create Date,,>
— Description: <Description,,>
— =============================================
CREATEPROCEDURE spVendorByState
@VendorState varchar(50)
AS
BEGIN
— SET NOCOUNT ON added to prevent extra result sets from