sqlzoo答案--join

1.

第一個例子列出球員姓氏為'Bender'的入球數據。 * 表示列出表格的全部欄位，簡化了寫matchid, teamid, player, gtime語句。

修改此SQL以列出 賽事編號matchid 和球員名 player ,該球員代表德國隊Germany入球的。要找出德國隊球員，要檢查: teamid = 'GER'

SELECT matchid ,player
FROM goal
WHERE teamid = 'GER'

 
2.

由以上查詢，你可見Lars Bender's 於賽事 1012入球。.現在我們想知道此賽事的對賽隊伍是哪一隊。

留意在 goal 表格中的欄位 matchid ，是對應表格game的欄位id。我們可以在表格 game中找出賽事1012的資料。

只顯示賽事1012的 id, stadium, team1, team2

SELECT id,stadium,team1,team2
FROM game
where id=1012

3.

我們可以利用JOIN來同時進行以上兩個步驟。

SELECT *
  FROM game JOIN goal ON (id=matchid)

語句FROM 表示合拼兩個表格game 和 goal的數據。語句 ON 表示如何找出 game中每一列應該配對goal中的哪一列 -- goal的 id 必須配對game的 matchid 。 簡單來說，就是
ON (game.id=goal.matchid)

以下SQL列出每個入球的球員(來自goal表格)和場館名(來自game表格)

修改它來顯示每一個德國入球的球員名，隊伍名，場館和日期。

SELECT player,teamid,stadium,mdate
FROM game JOIN goal ON (id=matchid)
where teamid = 'GER'

4.

使用上題相同的 JOIN語句，

列出球員名字叫Mario (player LIKE 'Mario%')有入球的 隊伍1 team1, 隊伍2 team2 和 球員名 player

select team1,team2,player
from goal join game on (id=matchid)
where player LIKE 'Mario%'

5.

表格eteam 貯存了每一國家隊的資料，包括教練。你可以使用語句 goal JOIN eteam on teamid=id來合拼 JOIN 表格goal 到 表格eteam。

列出每場球賽中首10分鐘gtime<=10有入球的球員 player, 隊伍teamid, 教練coach, 入球時間gtime

SELECT player, teamid,coach, gtime
FROM goal join eteam on (teamid=id)
WHERE gtime<=10

6.

要合拼JOIN 表格game 和表格 eteam，你可以使用
game JOIN eteam ON (team1=eteam.id)
或
game JOIN eteam ON (team2=eteam.id)

注意欄位id同時是表格game 和表格 eteam的欄位，你要清楚指出eteam.id而不是只用id

列出'Fernando Santos'作為隊伍1 team1 的教練的賽事日期，和隊伍名。

select mdate,teamname
from game JOIN eteam ON (team1=eteam.id)
where coach='Fernando Santos'

7.

列出場館 'National Stadium, Warsaw'的入球球員。

select player
from goal join game on (matchid=id)
where stadium in ('National Stadium, Warsaw')

8.

以下例子找出德國-希臘Germany-Greece 的八強賽事的入球

修改它，只列出全部賽事，射入德國龍門的球員名字。

HINT

select distinct player
from goal join(select id from game
where team1='GER' or team2='GER') t on (matchid=id)
where teamid !='GER'

9.

列出隊伍名稱 teamname 和該隊入球總數

select teamname,count(matchid)
from(SELECT teamname, matchid
FROM eteam JOIN goal ON (id=teamid)) t
group BY teamname

10.

列出場館名和在該場館的入球數字。

select stadium,count(player)
from (select stadium,player
from game join goal on (id=matchid)) t
group by stadium

11.

每一場波蘭'POL'有參與的賽事中，列出賽事編號 matchid, 日期date 和入球數字。

select matchid,mdate,count(teamid)
from(SELECT matchid,mdate, team1, team2,teamid
FROM game JOIN goal ON matchid = id
WHERE (team1 = 'POL' OR team2 = 'POL')) t
group by matchid,mdate

12.

每一場德國'GER'有參與的賽事中，列出賽事編號 matchid, 日期date 和德國的入球數字。

select matchid,mdate,count(teamid)
from(SELECT matchid,mdate, team1, team2,teamid
FROM game JOIN goal ON matchid = id
WHERE (team1 = 'GER' OR team2 = 'GER')) t
where teamid='GER'
group by matchid,mdate

13.

List every match with the goals scored by each team as shown. This will use "CASE WHEN" which has not been explained in any previous exercises.

mdate	team1	score1	team2	score2
1 July 2012	ESP	4	ITA	0
10 June 2012	ESP	1	ITA	1
10 June 2012	IRL	1	CRO	3
...

Notice in the query given every goal is listed. If it was a team1 goal then a 1 appears in score1, otherwise there is a 0. You could SUM this column to get a count of the goals scored by team1. Sort your result by mdate, matchid, team1 and team2.

SELECT mdate,
team1,
sum(CASE WHEN teamid=team1 THEN 1 ELSE 0 end) score1,team2,sum(case when teamid=team2 then 1 else 0 end) score2
FROM game JOIN goal ON (matchid = id)
group by mdate,matchid,team1,team2

/*sum可以直接括 case when ，group by可以有select中没有查询的字段*/

Old JOIN Tutorial

1.

Show the athelete (who) and the country name for medal winners in 2000.

SELECT who, country.name
FROM ttms JOIN country
ON (ttms.country=country.id)
WHERE games = 2000

2.

Show the who and the color of the medal for the medal winners from 'Sweden'.

ttms(games,color,who,country)
country(id,name)   

select who,color
from ttms join country
on (ttms.country=country.id)
where name='Sweden'

3.

Show the years in which 'China' won a 'gold' medal.

ttms(games,color,who,country)
country(id,name)   

select games
from ttms join country
on (ttms.country=country.id)
where color='gold' and name='China'

4.

Show who won medals in the 'Barcelona' games.

ttws(games,color,who,country)
games(yr,city,country)   

SELECT who
FROM ttws JOIN games
ON (ttws.games=games.yr)
WHERE city = 'Barcelona'

5.

Show which city 'Jing Chen' won medals. Show the city and the medal color.

ttws(games,color,who,country)
games(yr,city,country)   

select city,color
FROM ttws JOIN games
ON (ttws.games=games.yr)
where who='Jing Chen'

6.

Show who won the gold medal and the city.

ttws(games,color,who,country)
games(yr,city,country)   

select who,city
FROM ttws JOIN games
ON (ttws.games=games.yr)
where color='gold'

7.

Show the games and color of the medal won by the team that includes 'Yan Sen'.

ttmd(games,color,team,country)
team(id,,name)   

select games ,color
from ttmd join team
on (team=id)
where name like '%Yan Sen%'

8.

Show the 'gold' medal winners in 2004.

ttmd(games,color,team,country)
team(id,,name)   

select name
from ttmd join team
on (team=id)
where games='2004'and color='gold'

9.

Show the name of each medal winner country 'FRA'.

ttmd(games,color,team,country)
team(id,,name)   

select name
from ttmd join team
on (team=id)
where country='FRA'