# Difference between revisions of "Window functions"

General Elections were held in the UK in 2015 and 2017. Every citizen votes in a constituency. The candidate who gains the most votes becomes MP for that constituency.

## Warming up

Show the lastName, party and votes for the constituency 'S14000024' in 2019.

```SELECT lastName, party, votes
FROM ge
WHERE constituency = 'E14000539' AND yr = 2017
```
```SELECT lastName, party, votes
FROM ge
WHERE constituency = 'S14000024' AND yr = 2017
```

## Who won?

You can use the RANK function to see the order of the candidates. If you RANK using (ORDER BY votes DESC) then the candidate with the most votes has rank 1.

Show the party and RANK for constituency S14000024 in 2017. List the output by party
```SELECT party, votes,
RANK() OVER (ORDER BY votes DESC) as posn
FROM ge
WHERE constituency = 'E14000539' AND yr = 2017
```
```SELECT party, votes,
RANK() OVER (ORDER BY votes DESC) as posn
FROM ge
WHERE constituency = 'S14000024' AND yr = 2017
ORDER BY party
```

## PARTITION BY

The 2015 election is a different PARTITION to the 2017 election. We only care about the order of votes for each year.

Use PARTITION to show the ranking of each party in S14000021 in each year.
```SELECT yr,party, votes,
RANK() OVER (PARTITION BY yr ORDER BY votes DESC) as posn
FROM ge
WHERE constituency = 'S14000021'
ORDER BY party,yr
```
```SELECT yr,party, votes,
RANK() OVER (PARTITION BY yr ORDER BY votes DESC) as posn
FROM ge
WHERE constituency = 'S14000021'
ORDER BY party,yr
```

## Edinburgh Constituency

Edinburgh constituencies are numbered S14000021 to S14000026.

Use PARTITION BY constituency to show the ranking of each party in Edinburgh in 2017. Order your results so the winners are shown first, then ordered by constituency.
```SELECT constituency,party, votes
FROM ge
WHERE constituency BETWEEN 'S14000021' AND 'S14000026'
AND yr  = 2017
```SELECT constituency,party, votes,