1. NURS6803 Clinical DB Design Katherine Sward, PhD, RN
Even more SQL…
NURS6803
Clinical DB Design
Katherine Sward, PhD, RN 1

2. Union queries
Up to this point we joined tables horizontally, with additional columns
select demog.pt_id, name, rbc, wbc
from demog, blood
where demog.pt_id = blood.pt_id
pt_id
name
rbc
wbc 10
Brown, Mike
5.62
9.4
102
Costner, Kevin
3.32 16
3.55 12
103
Cole, Nat-King
4.39
5.8
3.36
3.7
104
Mason, Perry
4.05
7.5
105
Go, King-Fung 5
109
Bond, James
4.24

3. Union queries student (unid, lastname, firstname, email, major)
faculty (unid, lastname, firstname, , department)
Get a list of unid, name, and for all students and faculty
Process: create a query for each table, then paste the results together vertically into a single list
that is a UNION query

4. Union queries
SELECT unid, lastname, firstname , ‘student’ as PersonType
FROM students
UNION
SELECT unid, lastname, firstname, , ‘faculty’ as PersonType
FROM faculty;
unid
lastname
firstname
PersonType u
Smith
Sam
student u
Jones
Joe u
Anders
Sally u
Williams
Greg
faculty
Dodge
Kathy

5. Union queries Queries must be “Union compatible”
return same structure – same number of columns, matching data types (convert if necessary)
columns should conceptually match

6. Self join
Recursive relationship: there is a relationship between different rows in the same table

7. Table data employeeID name dateOfHire managerID u0000001 Bossman, Bob
1/1/2005 u
Overseer, Susie
1/2/2005 u
Worker, William
2/1/2005 u
Smith, Sam u
Jones, Jenny
8/15/2010 u
Little, Larry
8/21/2011 u
Mann, Macho
7/17/2006 u
Pipsqueak, Pippy
4/15/2007 u
Doer, Danny
6/6/2006 u
Jones, Jeff
2/8/2009

8. Self join Who are Susie’s employees? or
Show the ID and name for an employee, and the name of the employee’s manager

9. employeeID
name
dateOfHire
managerID u
Bossman, Bob
1/1/2005 u
Overseer, Susie
1/2/2005 u
Worker, William
2/1/2005 u
Smith, Sam u
Jones, Jenny
8/15/2010 u
Little, Larry
8/21/2011 u
Mann, Macho
7/17/2006 u
Pipsqueak, Pippy
4/15/2007 u
Doer, Danny
6/6/2006 u
Jones, Jeff
2/8/2009

10. Self join Process: pretend there are two copies of the table
Use the table name twice
Alias at least one of the copies
Join the tables (managerID as FOREIGN KEY)
Employee (Copy 1: Emp)
employeeID
name
dateOfHire
managerID
Employee (Copy 2: Mgr)
employeeID
name
dateOfHire
managerID M

11. Self join SELECT EMP.employeeID, EMP.name, MGR.name
FROM employee as EMP, employee as MGR
WHERE EMP.managerID = MGR.employeeID
employeeID
EMP.name
MGR.name u
Overseer, Susie
Bossman, Bob u
Worker, William u
Little, Larry u
Mann, Macho u
Jones, Jeff u
Smith, Sam u
Jones, Jenny u
Pipsqueak, Pippy u
Doer, Danny

12. Multiple relationships
Normally there is ONE relationship between two tables (that goes both directions)
Occasionally there is actually two relationships between the tables
Different “roles”

13. Multiple relationships
Suppose you had a database tracking baseball games
You have a “Teams” table and a “games” table
A team can participate in a game as the “home” team, OR a team can participate in a game as the “away” team (but never both at the same time).
These are two separate relationships

14. Table structure Team (TeamID, TeamName, Mascot)
BallGame (GameID, GameDate, Location, HomeTeamID, HomeScore, AwayTeamID, AwayScore)
To find the names for teams participating in a game, you need to get one row of data from the Teams table to get the name of the home team, and a different row of data in the teams table to get the name of the away team.

15. Process Like with did with self join
Pretend like the Team table exists twice

16. Ballgame
GameID
GameDate
Location
HomeTeamID
HomeScore
AwayTeamID
AwayScore
Team
TeamID
TeamName
Mascot
Team
TeamID
TeamName
Mascot

17. The query Select GameID, GameDate, H.TeamName As HomeTeam,
A. TeamName as AwayTeam
From BallGame AS G
Team AS H
Team AS A
Where G.HomeTeamID = H.TeamID  link the home copy
and G. AwayTeamID = A.TeamID;  link the away copy

18. Multiple functions
Let’s look at the demog table in the SNDB. It’s structure is
Demog (pt_id, name, zip, gender, race).
We need to know what’s the highest pt_id in the table. However, every column in this table was created as a TEXT field. So we can’t just sort the table and scan for the last entry – the data will sort alphabetically, so 1001 will show up early in the list, but 999 will show up late in the list.

19. Multiple functions
We can use a data type conversion function to pretend that the pt_id is a number. (Like we did with sorting data).
Cint(pt_id) or to_number(pt_id)
Access Oracle

20. Multiple functions
Then once we have it as a number, we can find the maximum value using the max() function
Those functions can be nested together. Just be careful to do the parentheses correctly.
SELECT max(cint(pt_id)) from demog;
If I run this, I see that the highest pt_id in my table is 1255 (your copy may differ slightly).

21. finally READ the description of other DML query types
Insert (add row of data)
Update (change existing row)
Delete (get rid of a row of data)