1. There’s a particular style to it…
SQL Style
There’s a particular style to it…
Rob Hatton

2. SQL is not a complete language
No way to build a user interface
No way to read or write to a file
Can’t print
Can’t control how things happen
It’s awesome at retrieving data!

3. SQL Server has 2 languages
ANSI SQL
Declarative
TSQL
Procedural
We’ll be talking about ANSI SQL
Focus on sets is the most important concept of the day!

4. SQL is a different kind of language
Most languages are procedural
Like telling a story
It’s the reason for TSQL
SQL is a declarative language
Like painting a picture
Based on Sets
It’s conceptually intertwined with Relational Database structure.
Sets are key to understanding SQL

5. Sets They’re just collections of values: Database Examples:
Customers that owe you money
Students & grades
Cities and temperatures
Database Examples:
Tables
Views
Sub-queries
Function return
Common Table Expressions (sort of)

6. Types Of SQL Statements
Data Definition Language (DDL)
Create (Table, View, Proc)
Alter (Table, View, Proc)
Drop (Table, View, Proc)
Data Manipulation Language (DML)
Select
Insert
Delete
Update
Database definition is stored in a database. DDL manipulates the definition.
We’re not going to focus on DDL.

7. Select Syntax SELECT field_list [ FROM set_source ]
(includes joins)
[ WHERE search_expression ] (record based)
[ GROUP BY group_expression ]
[ HAVING aggregate_expression ]
[ ORDER BY order_expression [ ASC | DESC ] ]
Where clause logic is record based, not set based!
‘Where eyeColor = ‘blue’ and eyeColor = ‘green’ returns no records.
‘Group by’ requires an aggregate function in select list.
‘Having’ only works with group by.
Where clause logic is record based, not set based!
‘Where eyeColor = ‘blue’ and eyeColor = ‘green’ returns no records.
‘Group by’ requires an aggregate function in select list.
‘Having’ only works with group by.

8. Functions and Expressions
UPPER() - Converts a field to upper case
SUBSTR() - Returns part of a character expression
LTRIM() – Remove spaces from left end of text field
LEN() - Returns the length of a text field
GETDATE() - Returns the system date and time
CHARINDEX() – Returns start of string in another string
Case When
Beware of misuse

9. Comparison Operators = < <= > <> ! (not) Between ExistsIn
Is [not] null
Remember, they are record based not set based!

10. The importance of NULL NULL is missing data
NULL is not the same as zero
Needed to calculate valid aggregates
Example:
When calculating average dress size, it keeps the guys from spoiling the average
Anything combined with a NULL is NULL
Any relational operator using a NULL returns NULL
The ISNULL() function helps deal with NULLs

11. Aliasing select fis.orderDateKey , max(fis.salesAmount) as maxAmt
from factInternetSales fis
group by fis.orderDateKey
Table Alias: fis
Field Alias: maxAmt

12. Stuff you’ll want * Entity Relationship Diagram (ERD)
Picture of database structure
Shows Primary/Foreign Keys
Management studio
Object Explorer
Intellisence
Drag and drop field names *

13. It’s important to understand data!
Query system tables
Profile data
--Profile
varchar(700)
varchar(50)
varchar(50)
varchar(100)
= ''
= ''
varchar(200)
DROP TABLE [dbo].[dbProfile]
IF EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[dbProfile]') AND type in (N'U'))
--Recreate the profile table
CREATE TABLE [dbo].[dbProfile](
[recordCnt] [int] NULL,
[ColumnName] [varchar](50) NOT NULL,
[TableName] [varchar](50) NOT NULL,
[distinctCnt] [int] NULL,
[fldSample] varchar(300)
[NullCnt] [int] NULL,
[nonNullCnt] [int] NULL,
) ON [PRIMARY]
SELECT t.name AS table_name,
declare dbSchema cursor for
c.name AS column_name
ORDER BY table_name
INNER JOIN sys.columns c ON t.OBJECT_ID = c.OBJECT_ID
FROM sys.tables AS t
while = 0
fetch next from
open dbSchema
begin
EXEC
= 'declare fldList cursor for select distinct ' + ' from '
open fldList
fetch next from fldList
while = 0 and < 200
+ + ', '
end
deallocate fldList
close fldList
= 'insert into dbProfile (TableName, ColumnName, recordCnt, distinctCnt, nonNullCnt, nullCnt, fldSample) '
+'count(distinct as distinctCnt, '
+'count(*) as recordCnt, '
+'select as TableName as ColumnName, '
+ '''' + + ''''
+'sum(case when 0 then 1 else 0 end) as NullCnt, '
+'sum(case when 0 then 0 else 1 end) as nonNullCnt, '
+' from '
begin try
end try
end catch
begin catch
deallocate dbSchema
close dbSchema
select * from dbProfile *

14. Joins
Based on values in one table (usually a primary key) matching values in another table (usually a foreign key)
Types
Inner
Outer
Left
Right
Cross
Full
Self
Exists
Joins work with any comparison operator!
Joins aren’t as much of a problem as data size!
--Example Queries go
use Fruit
select * from fruit
select * from colors
from fruit
select *
--Use 'where' clause
where colorKey = 1
--Dealing with null
where colorKey is null
--where colorKey = null
--Wildcard
--where fruitName like '%e '
where fruitName like '%e%'
--where rtrim(fruitName) like '%e'
--'In' clause
where fruitName in ('apple','grape')
--In with a subquery
where fruitName in (select fruitName from fruit where rtrim(fruitName) like '%e')
--Everything from inner join
from fruit f
--Relevent columns from inner join
on f.colorKey = c.colorKey
inner join colors c
select f.fruitName, c.color
--Everything from left outer join
left outer join colors c
--Everything from right outer join
right outer join colors c
--Everything from Cross join (match everything with everything - no 'on' condition)
--on f.colorKey = c.colorKey
cross join colors c
--Everything from full join (combination of left & right outer joins)
full join colors c
select fruitName
--Check for Exists
(select *
where exists
from colors c
--Alternate version of Exists
where c.colorKey = f.colorKey)
where f.colorKey is not null
on c.colorKey = f.colorKey
select colorKey, count(*) as cnt
--Aggregations
having count(*) > 1
group by colorKey
use [AdventureWorksDW]
--Self join
from DimAccount c
select c.AccountDescription, p.AccountDescription
order by c.accountKey
on p.ParentAccountKey = c.AccountKey
left outer join DimAccount p *

15. Demo Database Fruit Database Colors table Fruit table Red Yellow Green
Orange
Fruit table
Banana
Grape
Apple
Eaten

16. Common Table Expressions
CTE
Create a set on the fly
Can only be used in a single query
Doesn’t actually create the set
Think of it like an include
Optimizer doesn’t see a separate set
--Common Table Expressions
with northAmerica as
(select [SalesTerritoryKey], [SalesTerritoryRegion]
from DimSalesTerritory
where [SalesTerritoryGroup] = 'North America')
select top 3 na.SalesTerritoryRegion, fis.SalesAmount
from FactInternetSales fis
inner join northAmerica na
on na.SalesTerritoryKey = fis.SalesTerritoryKey *

17. Union * Combine 2 sets with matching fields Useful in replacing Case
Field count must match exactly
Data types must be implicitly convertible
First query dictates names
Useful in replacing Case
Implicitly removes duplicates
Use ‘Union All’ to preserve duplicates
--Union
use [AdventureWorksDW2012] Go
select distinct st.SalesTerritoryRegion
from FactInternetSales fis
inner join DimSalesTerritory st
on fis.SalesTerritoryKey = st.SalesTerritoryKey
union
from FactResellerSales frs
on frs.SalesTerritoryKey = st.SalesTerritoryKey *

18. There’s a particular style to it…
SQL Style
There’s a particular style to it…
Rob Hatton