SQL Where Archives - SQL Training Online

September 27, 2017 by Joey Blue Leave a Comment

SQL Joins Tutorial for Beginners – Inner Join, Left Join, Right Join, Full Outer Join – SQL Training Online

How to write SQL Joins in 10 minutes. (*Plus another 8 minutes of bonus material.)

Learn how to create SQL Joins. The first 10 minutes teach you the basics. Inner Join, Left Outer Join, Right Outer Join, and Full Outer Join. The second 10 minutes show you are few techniques that will help you as you start building joins.

Video: SQL Join Tutorial

How to write SQL Joins in 10 minutes.

The following Scripts are used in the training:

--Create Customer Table
CREATE TABLE [dbo].[Customer](
	[CustomerId] [int] NOT NULL,
	[CityId] [int] NULL,
	[CustomerName] [varchar](50) NOT NULL
) ON [PRIMARY]
GO
--Insert Customer Records
INSERT [dbo].[Customer] ([CustomerId], [CityId], [CustomerName]) VALUES (1, 1, N'Bob Smith')
GO
INSERT [dbo].[Customer] ([CustomerId], [CityId], [CustomerName]) VALUES (2, 1, N'Sally Smith')
GO
INSERT [dbo].[Customer] ([CustomerId], [CityId], [CustomerName]) VALUES (3, 2, N'Tom Smith')
GO
INSERT [dbo].[Customer] ([CustomerId], [CityId], [CustomerName]) VALUES (4, NULL, N'Mary Smith')
GO
--Create City Table
CREATE TABLE [dbo].[City](
	[CityId] [int] NOT NULL,
	[CityName] [varchar](50) NOT NULL
) ON [PRIMARY]
GO
--Insert City Records
INSERT [dbo].[City] ([CityId], [CityName]) VALUES (1, N'Kansas City')
GO
INSERT [dbo].[City] ([CityId], [CityName]) VALUES (2, N'New York')
GO
INSERT [dbo].[City] ([CityId], [CityName]) VALUES (3, N'Houston')
GO

See the original SQL Join Tutorial for Beginners video.

September 13, 2017 by Joey Blue 2 Comments

Learn Basic SQL – 1 Hour Training Course – SQL Training Online

How to write SQL from scratch in 1 hour.

**Full Beginner’s Course**

In this video I show you how to write SQL using SQL Server and SQL Server Management Studio. We go through Creating a Database, Creating Tables, Inserting, Updating, Deleting, Selecting, Grouping, Summing, Indexing, Joining, and other basics you need to get starting writing SQL.

Video: Learn Basic SQL

How to write SQL from scratch in 1 hour.

The following Scripts are used in the training:

--Create Database
Create Database Customer;

--Create Customer Table
create table Customer
(
	FirstName varchar(50),
	LastName varchar(50),
	Age int
);

--Insert Initial Data
insert into Customer (FirstName,LastName,[Age]) values ('Joey','Blue',40);
insert into Customer (FirstName,LastName,[Age]) values ('Barry','Bonds',50);
insert into Customer (FirstName,LastName,[Age]) values ('Mike','Schmidt',60);
insert into Customer (FirstName,LastName,[Age]) values ('Mike','Schmidt1',61);
insert into Customer (FirstName,LastName,[Age]) values ('Mike','Schmidt2',62);
insert into Customer (FirstName,LastName,[Age]) values ('Mike','Schmidt3',63);
insert into Customer (FirstName,LastName,[Age]) values ('Mike','Schmidt4',64);
insert into Customer (FirstName,LastName,[Age]) values ('Mike','Schmidt5',65);

--This deletes mike schmidt
/*
DELETE Customer
where FirstName='Mike'
and LastName Like 'Schmidt_';
*/

--Select Mike Schmidt
select *
from Customer
where FirstName='Mike'
and LastName Like 'Schmidt_';

--Update City on Barry Bonds
update Customer
Set City='Goddard'
where FirstName='Barry'
and LastName = 'Bonds' ;

--Add City to the Customer Table
alter table customer
add City varchar(50);

--Drop the Customer Table
drop table customer;

--Create Customer Table with Primary Key
create table Customer
(
	Id int Primary Key identity(1,1),
	FirstName varchar(50),
	LastName varchar(50),
	Age int,
	City varchar(50)
)

--Insert Customer Data
insert into Customer 
(FirstName,LastName,[Age],City) values ('Joey','Blue',40, 'Goddard');
insert into Customer 
(FirstName,LastName,[Age],City) values ('Barry','Bonds',50, 'San Francisco');
insert into Customer 
(FirstName,LastName,[Age],City) values ('Mike','Schmidt',60, 'KC');

--Create Products Table
create table Products
(
	id int primary key identity(1,1),
	ProductName varchar(50)
)

--Add Price to Products Table
alter table Products
add Price float;

--Select everything from Products table
select * from Products

--Insert Products
insert into Products (ProductName, Price) values ('Baseball', 5.95);
insert into Products (ProductName, Price) values ('Bat', 195.99);

--Create Orders Table
Create table Orders
(
	OrderId int primary key identity(1,1),
	OrderDate Datetime,
	CustomerID int,
	ProductID int
)

--Insert Orders
insert into Orders (OrderDate,CustomerID,ProductID) values (GetDate(),1,1);
insert into Orders (OrderDate,CustomerID,ProductID) values (GetDate(),1,1);
insert into Orders (OrderDate,CustomerID,ProductID) values (GetDate(),2,1);
insert into Orders (OrderDate,CustomerID,ProductID) values (GetDate(),2,1);
insert into Orders (OrderDate,CustomerID,ProductID) values (GetDate(),2,2);
insert into Orders (OrderDate,CustomerID,ProductID) values (GetDate(),2,2);
insert into Orders (OrderDate,CustomerID,ProductID) values (GetDate(),2,2);
insert into Orders (OrderDate,CustomerID,ProductID) values (GetDate(),2,2);
insert into Orders (OrderDate,CustomerID,ProductID) values (GetDate(),3,2);
insert into Orders (OrderDate,CustomerID,ProductID) values (GetDate(),3,2);
insert into Orders (OrderDate,CustomerID,ProductID) values (GetDate(),4,2); --Bad Record

--Select from Tables
select * from Orders;
select * from Products;
select * from Customer;

--Delete Bad Order  **Your OrderId may be different
delete Orders
where OrderId=21;

--Add Foreign Keys to the Orders table
alter table orders
add foreign key (CustomerId) references Customer(Id);

alter table orders
add foreign key (ProductId) references Products(Id);

--Find the Total and Average Price per City
select c.City,sum(p.Price),AVG(p.price) Total
from Orders o 
inner join Products p on o.ProductID=p.id
inner join Customer c on o.CustomerID=c.Id
group by c.City

See the original SQL Training Course for Beginners video.

August 27, 2017 by Joey Blue 1 Comment

Moving Average with Windowing in SQL Server

The Moving Average used to be complex, but with the Windowing Functions, the Moving Average is easier and performs much better.

In this video I show you how to create a moving average in SQL using the OVER Clause and the ROWS Clause.

Video: SQL Moving Average with Windowing

How to use the SQL Over Clause for a Moving Average.

I use the Wide World Importers and the following scripts:

select [Invoice Date Key], sum(Profit) Profit
into dbo.ProfitByDate
from [Fact].[Sale]
group by [Invoice Date Key];

select 
[Invoice Date Key],
avg(Profit) OVER (ORDER BY [Invoice Date Key] ROWS BETWEEN 4 PRECEDING AND CURRENT ROW) as AverageProfit
from dbo.ProfitByDate
order by 1

Link to the Microsoft SQL Server Over Clause.

See the original SQL Rolling Average with Windowing video.

August 26, 2017 by Joey Blue Leave a Comment

Format Function in SQL Server

The Format Function can help you change how a date or decimal is displayed.

In this video I do a quick demonstration of the Format Function.

Video: SQL Server Format Function

How to use the SQL Format Function on a Date.

I use the Wide World Importers and the following scripts:

select OrderDate,Format(OrderDate,'MMM dd, yyyy') 
from [Sales].[Orders]
where year(OrderDate) = 2016

Link to the Microsoft SQL Server Custom Date Formatters.

See the original SQL Format for Date video.

November 5, 2012 by Joey Blue Leave a Comment

How to Filter for SQL Null or Empty String

Video: How to Filter for SQL Null or Empty String – SQL Training Online
In this video, I show you how to filter a SQL table that has both Null values and an Empty string. I use SQL Server 2012 to demonstrate the technique.

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How do you filter a SQL Null or Empty String?

A null value in a database really means the lack of a value. It is a special “value” that you can’t compare to using the normal operators. You have to use a clause in SQL IS Null.

On the other hand, an empty string is an actual value that can be compared to in a database. You simply use two ticks together.

''

Let’s take a look at the vendor table to demonstrate this.

select * from vendor

In this table, I specifically put in some email addresses that are both null and empty strings.

Let’s pull out the NULL values using the IS NULL operator.

select * from vendor
where vendor_email is null

Next, I want to pull out the empty string using the tick-tick, or empty string.

select * from vendor
where vendor_email = ''

If you want to combine them to search for the SQL null or empty string together and retrieve all of the empty strings and nulls all at once, you could do something like this.

select * from vendor
where vendor_email = ''
or vendor_email is null

Finally, I want to show you a little trick that I have used on occasion to change all of the null values to empty strings and then compare the result to an empty string.

select * from vendor
where isnull(vendor_email,'') = ''

And that is it.

Here is the script to create the vendor table I was using as an example.

create table dbo.vendor
(
vendor_id int identity(1,1) primary key,
vendor_name varchar(50),
vendor_email varchar(100)
)
insert into vendor (vendor_name,vendor_email) values ('Dell','[email protected]');
insert into vendor (vendor_name,vendor_email) values ('IBM','[email protected]');
insert into vendor (vendor_name,vendor_email) values ('Microsoft','[email protected]');
insert into vendor (vendor_name,vendor_email) values ('Oracle','');
insert into vendor (vendor_name,vendor_email) values ('Intel',NULL);
insert into vendor (vendor_name,vendor_email) values ('Apple','[email protected]');

There it is. That is how you filter for SQL Null or Empty String.

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