Nested Select Statement in SQL Server
In SQL Server, a Nested Select statement is essentially a select statement contained within another select statement. This structure comprises a parent query and a subquery. Typically, the outcome of the parent query relies on the results of the subquery. Nested select statements are commonly utilized for filtering results, a fundamental requirement in various data analysis tasks. They allow us to refine and narrow down the data set based on specific criteria, contributing to more precise and insightful analyses.
Syntax:
SELECT column_name_1
FROM table_name_1
WHERE column_name_1 = (SELECT column_name_2 FROM table_name_2);
Create a Table and Insert data
First, we will have to create at least two tables in the database to understand the examples of nested select statements in SQL Server. To create the tables in the database we will have to perform the following quires:
Query to create first table.
Query:
CREATE TABLE employee (
EmployeeID INTEGER,
FirstName VARCHAR(100),
LastName VARCHAR(100),
DepartmentID INTEGER,
Position VARCHAR(100),
Salary DECIMAL(10, 2)
);
Query to create second table.
Query:
CREATE TABLE Department (
DepartmentID INT PRIMARY KEY,
DepartmentName VARCHAR(100)
);
Now that our tables are created, we have to insert data into our tables. To insert data into our tables we will write and run the following quires.
Inserting data in 1st table
To insert data in first table write the following query:
Query:
INSERT INTO Employee (EmployeeID, FirstName, LastName, DepartmentID, Position, Salary)
VALUES
(1, 'John', 'Doe', 1, 'Sales Representative', 50000.00),
(2, 'Jane', 'Smith', 2, 'Marketing Manager', 75000.00),
(3, 'Michael', 'Johnson', 1, 'Sales Manager', 80000.00),
(4, 'Emily', 'Williams', 3, 'HR Specialist', 60000.00),
(5, 'David', 'Brown', 4, 'Financial Analyst', 70000.00);
Output:
Inserting data in 2st table
To insert data in second first table write the following query:
Query:
INSERT INTO Department (DepartmentID, DepartmentName)
VALUES
(1, 'Sales'),
(2, 'Marketing'),
(3, 'Human Resources'),
(4, 'Finance');
Output:
What is Nested Select Statement in SQL Server
SQL Server is a powerful relational database management system. Sql Server is very good with its robustness and scalability. SQL Server operates as a client-server structure, imparting centralized management and scalability for huge-scale applications and enterprise-stage solutions. It offers advanced features which include excessive availability, protection, and extensive support for complex data operations.
In this article, we will go to cover the nested select statements in SQL Server, unraveling their functionality and demonstrating their versatility through complete examples and use cases.