Tutorial (12) Select Statement in SQL

Tutorial (12) Select Statement in SQL

Tutorial 12 Select Statement in SQL with example

 SQL stands for Structured Query Language, and it is a standard language for accessing and manipulating databases.

 It is used to manage and retrieve data from relational database management systems (RDBMS). Here’s an example of a simple SQL query:

 Suppose we have a table named “Employees” with the following columns: “EmployeeID”, “FirstName”, “LastName”, “Department”, and “Salary”. Here’s an example of a basic SQL query to retrieve data from this table:

SELECT FirstName, LastName, Department, Salary

FROM Employees;

 This SQL query selects the “FirstName,” “LastName,” “Department,” and “Salary” columns from the “Employees” table. The “SELECT” statement is used to specify the columns that you want to retrieve from the table. The “FROM” clause specifies the table from which the data is to be retrieved.

 You can further refine your query using various clauses such as “WHERE” for filtering data, “ORDER BY” for sorting the results, “GROUP BY” for grouping data, and “JOIN” for combining data from multiple tables, among others. SQL is a powerful language that allows users to perform complex operations on databases efficiently.

SELECT statement in SQL with Example

 The SELECT statement in SQL is used to retrieve data from a database. It allows you to specify the columns that you want to retrieve and can also include various other clauses to filter, sort, and group the data. Here’s a simple example of the SELECT statement in SQL:

 Suppose we have a table named “Customers” with the following columns: “CustomerID”, “FirstName”, “LastName”, “Email”, and “Phone”. We want to retrieve the customer names and email addresses from this table. The SQL query would look like this:

SELECT FirstName, LastName, Email

FROM Customers;

 This SELECT statement selects the “FirstName,” “LastName,” and “Email” columns from the “Customers” table. The FROM clause specifies the table from which the data is to be retrieved.

You can also use the SELECT statement with other clauses to make the query more specific.

 For example, you can use the WHERE clause to filter the results based on a condition, the ORDER BY clause to sort the results, and the LIMIT clause to limit the number of rows returned. Additionally, you can use aggregate functions like COUNT, SUM, AVG, and MAX to perform calculations on the data.

How to use linkd server in SQL query

To use a linked server in an SQL query, you first need to set up the linked server using SQL Server Management Studio. Here’s an example of how to set up a linked server to access data from another SQL Server:

EXEC sp_addlinkedserver  

   @server=’LinkedServerName’,

   @srvproduct=”,

   @provider=’SQLNCLI’,

   @datasrc=’ServerName’;

GO

In the above example:

@server is the name of the linked server that you want to create.

@srvproduct is the product name associated with the linked server.

@provider is the OLE DB provider name. In this case, it’s ‘SQLNCLI’ for SQL Server.

@datasrc is the data source, which is the name of the server you want to link to.

Once you have set up the linked server, you can use it in SQL queries. Here’s an example of a simple SQL query using a linked server:

SELECT *

FROM LinkedServerName.DatabaseName.SchemaName.TableName;

 In the above query, replace LinkedServerName, DatabaseName, SchemaName, and TableName with the appropriate names from your linked server.

 This query will allow you to retrieve data from the linked server and perform any necessary operations or joins.

Make sure you have the necessary permissions and configurations set up for the linked server to function properly.

How to create local server in sql server management studio

 To create a local server in SQL Server Management Studio (SSMS), you need to install and set up SQL Server on your local machine. Here are the general steps to create a local server in SQL Server Management Studio:

Install SQL Server: Download and install the appropriate version of SQL Server on your local machine. You can download it from the official Microsoft website or through the SQL Server installation media.

 Run SQL Server Installation: Launch the SQL Server installation and follow the installation wizard’s instructions. Make sure to select the appropriate configuration options, such as the instance name and authentication mode.

 Open SQL Server Management Studio (SSMS): After installing SQL Server, open SQL Server Management Studio. You can typically find it in the Start menu or by searching for “SQL Server Management Studio” in the search bar.

 Connect to the Local Server: In SSMS, you can connect to the local server by specifying the server name as either “localhost” or “.” (period). Choose the appropriate authentication method, such as Windows Authentication or SQL Server Authentication, and enter the necessary credentials.

 Once you have successfully connected to the local server, you can create databases, tables, views, and other database objects directly within SSMS. You can also run SQL queries, manage security settings, and perform various administrative tasks related to your local SQL Server instance.

what is query in SQL?

  In the context of SQL (Structured Query Language), a query refers to a request for data or information from a database. SQL queries are used to retrieve, insert, update, or delete data in a database.

A query can be as simple as selecting a specific column from a table or as complex as joining multiple tables and applying various conditions to filter the data.

Here are some common types of SQL queries:

SELECT query: Used to retrieve data from one or more tables.

Example:

SELECT column1, column2 FROM table_name;

INSERT query: Used to insert new records into a table.

Example:

INSERT INTO table_name (column1, column2) VALUES (value1, value2);

UPDATE query: Used to modify existing records in a table.

Example:

UPDATE table_name SET column1 = new_value1, column2 = new_value2 WHERE condition;

DELETE query: Used to remove records from a table.

Example:

DELETE FROM table_name WHERE condition;

 SQL queries can also involve complex operations like joins, subqueries, aggregations (using functions like SUM, AVG, COUNT, etc.), sorting (using ORDER BY), and filtering (using WHERE).

 Understanding SQL queries is crucial for effectively managing and manipulating data within a relational database management system (RDBMS).

SQL commands with example

  Sure, here are some common SQL commands with examples:

CREATE TABLE: Used to create a new table in the database.

CREATE TABLE Students (

    StudentID INT PRIMARY KEY,

    FirstName VARCHAR(50),

    LastName VARCHAR(50),

    Age INT

);

SELECT: Used to retrieve data from a database.

SELECT * FROM Students;

INSERT INTO: Used to insert new records into a table.

INSERT INTO Students (StudentID, FirstName, LastName, Age)

VALUES (1, ‘John’, ‘Doe’, 20);

UPDATE: Used to modify existing records in a table.

UPDATE Students

SET Age = 21

WHERE StudentID = 1;

DELETE FROM Students

WHERE StudentID = 1;

ALTER TABLE: Used to modify an existing table.

ALTER TABLE Students

ADD GPA DECIMAL(3, 2);

DROP TABLE: Used to delete an existing table.

DROP TABLE Students;

CREATE INDEX: Used to create an index on a table.

CREATE INDEX idx_lastname

ON Students (LastName);

ALTER TABLE ADD CONSTRAINT: Used to add a constraint to a table.

ALTER TABLE Students

ADD CONSTRAINT pk_Students PRIMARY KEY (StudentID);

GRANT: Used to give user access privileges to a database.

GRANT SELECT, INSERT ON Students TO user1;

These are some of the basic SQL commands used for creating, modifying, and manipulating data in a relational database management system (RDBMS). There are many other SQL commands available for more advanced database management and manipulation tasks.

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