The data includes all Members of the Scottish Parliament (MSPs) in 1999. Most MSPs belong to a political party. Some parties have a leader who is an MSP. There are two tables:
|Adam MSP, Brian||SNP||North East Scotland|
|Aitken MSP, Bill||Con||Glasgow|
|Alexander MSP, Ms Wendy||Lab||Paisley North|
|... Total number of records: 129|
|Con||Conservative||McLetchie MSP, David|
|Lab||Labour||Dewar MSP, Rt Hon Donald|
|... Total number of records: 9|
One MSP was kicked out of the Labour party and has no party. Find him.
You might think that the phrase dept=NULL would work here. It doesn't. This is because NULL "propogates". Any normal expression that includes NULL is itself NULL, thus the value of the expressions 2+NULL and party || NULL and NULL=NULL for example are all NULL.
NULL value does not cause a type error, however it does infect everything it touches with
NULL-ness. We call this element the
bottom value for the algebra - but we don't snigger because we are grown-ups. Bottom Type.
SELECT name FROM msp WHERE party IS NULL
Obtain a list of all parties and leaders.
SELECT name, leader FROM party
Give the party and the leader for the parties which have leaders.
SELECT name, leader FROM party WHERE leader IS NOT NUL
Obtain a list of all parties which have at least one MSP.
SELECT DISTINCT party.name FROM msp, party WHERE party=code
Obtain a list of all MSPs by name, give the name of the MSP and the name of the party where available. Be sure that
Canavan MSP, Dennis is in the list.
Use ORDER BY msp.name to sort your output by MSP.
SELECT msp.name, party.name FROM msp LEFT JOIN party ON party=code ORDER BY msp.name
Obtain a list of parties which have MSPs, include the number of MSPs.
SELECT party.name, COUNT(msp.name) FROM msp, party WHERE msp.party=party.code GROUP BY party.name
A list of parties with the number of MSPs; include parties with no MSPs.
SELECT party.name, COUNT(msp.name) FROM party LEFT JOIN msp ON party.code=msp.party GROUP BY party.name