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Tools of the trade
TSQL
CIS 407
SQL Server Tools
Books on line!
• Don’t use sql server authentication
– Use windows authentication (safer) for developer
version
• Don’t embed passwords in code (ways to avoid
this )
• Connection strings in appendix X (for accessing
with code
• Query window
– This is where we do almost everything using Tsql
statements (chapter 3)
– Not just queries – create update tables, system info,
etc
Query Window Example pg 33
• (follow along on your own machine)
• Open query window
• Select * from information-schema.tables
– Information_schema is a special access path for
displaying meta data about your system’s database
• Hit execute button
• Show execution plan
– Lots of stuff going on to convert SQL to code (loops,
ifthenelse, etc).
– Why do you care?
Transaction SQL
• Basic
– Select
– Insert
– Update
– Delete
Basic Select
• Syntax on page 42
• Use northwinds
• Select * from customers
– Select all the rows and columns from
customer relation
– Using * is expensive – better to specify only
those columns you want
• Select companyName from customers
– All rows but just the companyname column
from customers
Select Statement
• Select companyName from
northwinds.customers
– Can use database name before relation name
• Select companyName, contactName
from customers
where customerId = 23
– Page 48 details where clause operators
• =, =>, =<, <>, !=, !>, !<
• and, or, not, between, like, in, all, any, some,
exists
‘Where’ clause examples
• Select *
from customers
where (city=‘NY’ or city=‘detroit’) and
contactTitle = ‘boss’ or contactTitle >
‘flunky’
• select * from customers
where companyName in
(‘snufu’,’acme’,’fubar’)
‘Order by’ Clause
• Relations are sets of tuples or rows
– Sets are not ordered
– Cannot assume results of query will be
returned in any order !!!
• If want particular order, then MUST use
‘order by’ clause
– Expensive
• Select * from customers
where city = ‘ny’
order by companyName DESC, address
Aggregating data
• Select avg(unitPrice) as ‘averagePrice’
from product as p
where p.categoryID = 10
– note alias – ‘as’ optional
– Alias has other uses – more later
• Select count(customerID)
from customers c
where c.city = ‘NY’
• Aggregates: avg, min, max, count,
Aggregates and ‘group by’
• Aggregates for each value of specified col.
• Select orderID, min(quantity)
from [order details] (!!!!!)
where orderID between 11000 and 12002
group by orderID
Constraining Groups with ‘Having’
• Select employeeID, count(customerID)
from Orders
where shipCity = ‘ny’
having count <100
• List the number of customers with orders
shipped to NY for each employee but only
if the count is greater than 100.
• “where” constrains what goes into group
• ‘having” constrains what goes in result
Distinct
• Relations are sets and so should not have
duplicates.
• But removing duplicates in the results set
requires either a complex datastructure or
sorting (expensive)
– So SQL server does not do this unless you ask
• Select distinct city from customers
• Select count(distinct customerId)
from [order detail]
Insert statement (pg 66)
• Insert [into] <table> [(column_list)]
values (data_values)
• Insert shippers (shipperID, companyName,
Phone) values (1234,’acme’,’(208)2822685’)
• Listing columns optional: Insert shippers
values (1234,’acme’, ’(208)2822685’)
Insert Statement
• Not all columns need be listed (except
keys)
• Insert shippers (shipperid) values (1234)
– Nulls or defaults for the rest BUT much better
– Insert shippers (shipperID, companyName,
Phone) values (1234,default, null)
– Page 67: recommend naming every column
every time, even if have to use explicit null
and default – code more readable.
Nulls are BAD
• What does Null mean?
– Not supposed to be there?
– Unknown
• Exec sp_help <name>
page 69
Combine Insert & Select (pg71)
• Use Northwind
Declare @MyTable TABLE (
OrderID int,
CustomerID char(5) )
Insert into @mytable
select orderid, customerid
from Northwind.dbo.Orders
where OrderID between 10240 and 10250
select * from @mytable
Update Statement
• Update <table name>
set <column> = <value>
[,<column> = <value>]*
[from <source table(s)>]
[where <restrictive condition>]
• Update shippers
set companyName = ‘fubar’
where shipperID = 10
Delete Statement
• DELETE <table_Name>
where <search condition>]
• Delete customer where customerID = 10