Getting Started With Basic SQL Keywords And SQL Join

Introduction

This article starts with the basics of the SQL keyword. These keywords are for data filtration in a SQL database table.

From Command

Select * From TableName  
Select Column From TableName  

Example

select * from Info   
select Name from Info  

Where Command

Select * from TableName where Condition  
Select column1, column2 from TableName where Condition  

Example

select * from Info where City = 'Ahmedabad'  
select Name from Info where city = 'Surat' 

Top Command

This command selects the top rows in a database table.

Select Top value from TableName  

Example

select Top 3 * from Info   
select Top (25) percent * from Info  

As Command

Use for Alias Keyword.

Select ExitingColumnName AS NewAliasColumnName from TableName  

Example

Select Name From Info  
select Name AS [Person Name] from Info  

AND Command

select * from TableName where condition1 AND Condition2  
select ColumnName from TableName where condition1 AND Condition2  

Example

select * from Info where Name='Rakesh' And City= 'Ahmedabad'  
Select * From info where Name='Rakesh' And City = 'Surat'  

OR Command

select * from TableName where condition1 OR Condition2  
select ColumnName from TableName where condition1 OR Condition2  

Example

select * from Info where Name='Rakesh' OR City= 'Ahmedabad'  
Select * From info where Name='Rakesh' OR City = 'Surat'  

Between Command

Select * from TableName where columnCondition Between StartValue AND EndValue  

Example

select * from Info  
select * from info where id Between 3 AND 5  

IN Command

select * from TableName where condition IN (‘DATAValue’)  

Example

select * from Info where city in ('Ahmedabad')  
select * from Info where city in ('Goa','Surat')  

LIKE Command

select * from TableName From ColumnName LIKE ‘%VALUE%’  

Example

select * from Info where city like '%Goa%'  
Select * from Info Where City like '%Ahm%'  
Select * from Info where Name like '%esh%'  
Select * from Info where id like '%3%'  

Distinct Command

Don't display the same multiple records.

Select DISTINCT ColumnName From TableName  

Example

select City from Info  
Select DISTINCT City from Info  

Order By Command

Sorts data in ascending or descending order.

Select * from TableName Order By ColumnName ASC | DESC  
Select columnName from TableName Order By ColumnName ASC | DESC  

Example

Select * from Info order by Name ASC --ascending order by Name Column  
Select Name from Info order by Name DESC --descending order by Name Column  

Group By Command

Selects data in a group.

Select conditionwithcolumn from TableName Group by ColumnName  

Example

select city, count(Name) As Number_of_Person from Info Group by City  

Counts the total number of people in each city.

SQL Join

A join is the most important concept of SQL databases. In this, any two or more tables are joined with the same data column field. Many types of joins are available in SQL Server. 

Find a detailed article about joins in SQL Server here: Joins in SQL Server.

Basic Command

Select column1, column2   
From Table1  
[Type of Join] Table2   
ON condition  

Cross Join 

All data records are selected from the selected database table.

Command

Select column from Table1 CROSS JOIN Table2   

Example

select EmployeeData.EmployeeID,EmployeeData.EmployeeName,Department.Department  
from EmployeeData  
Cross Join Department  

If 5 data records are in Table1 and 2 in Table2, then in a cross join, the output is from both tables and is multiple records.

Example

[5 record * 2 record = Total 10 records display]

Inner Join

Command

Select Table1.column,  
Table2.column,  
From Table1   
Inner join Table2 ON Table1.ColumnID = Table2.ColumnID  

Example

select EmployeeData.EmployeeID,  
EmployeeData.EmployeeName,  
Department.Department  
From EmployeeData  
Inner Join Department  
ON EmployeeData.DepartmentID=Department.DepartmentID  

Outer Join

Two types of outer joins in SQL database.

Left Outer Join

Command

Select Table1.column,  
Table2.column,  
From Table1   
Left outer join Table2 ON Table1.ColumnID = Table2.ColumnID  

Example

select EmployeeData.EmployeeID,EmployeeData.EmployeeName,  
Department.DepartmentID,Department.Department  
From EmployeeData  
LEFT Outer Join Department  
ON EmployeeData.DepartmentID=Department.DepartmentID  

Right Outer Join

Command Example

Select Table1.column,  
Table2.column,  
From Table1   
Right outer join Table2 ON Table1.ColumnID = Table2.ColumnID  
select EmployeeData.EmployeeID,EmployeeData.EmployeeName,  
Department.DepartmentID,Department.Department  
From EmployeeData  
Right Outer Join Department  
ON EmployeeData.DepartmentID=Department.DepartmentID  

Union Command

Select column1, column2   
from Table1  
TypeofJoin Teble2  
ON Table1.ColumnID = Table2.ColumnID  
UNION   
Select column1, column2   
from Table1  
TypeofJoin Teble2  
ON Table1.ColumnID = Table2.ColumnID  

Example

Select EmployeeID,EmployeeName,Department  
From EmployeeData  
Left outer Join Department   
On EmployeeData.EmployeeID = Department.DepartmentID  
Union  
Select EmployeeID,EmployeeName,Department  
From EmployeeData  
Right outer Join Department   
On EmployeeData.EmployeeID = Department.DepartmentID  

Union ALL Command  

Select column1, column2   
from Table1  
TypeofJoin Teble2  
ON Table1.ColumnID = Table2.ColumnID  
UNION ALL  
Select column1, column2   
from Table1  
TypeofJoin Teble2  
ON Table1.ColumnID = Table2.ColumnID

Example

Select EmployeeID,EmployeeName,Department  
From EmployeeData  
Left outer Join Department   
On EmployeeData.EmployeeID = Department.DepartmentID  
Union ALL  
Select EmployeeID,EmployeeName,Department  
From EmployeeData  
Right outer Join Department   
On EmployeeData.EmployeeID = Department.DepartmentID

Summary

I hope you understand SQL database condition keywords and joins.

Reference

• Joins in SQL Server
• Types of Joins in SQL Server