帮助编写SQL查询

Question

我正在尝试编写一个查询，以获取表格中每个国家/地区的体育团队中的玩家数量：

我有一个包含以下字段的表

country | sports_team | player_name

我想要展示的是与此相似的结果

country | sports_team | number_of_players

即。我想遍历所有国家，并且对于sports_team的每一次变化，我都想记录团队中的球员数量。

样本表：

country | sports_team | player_name
c1      |  teamA      |  name1
c1      |  teamA      |  name2
c1      |  teamB      |  name3
c2      |  teamC      |  name4
c2      |  teamC      |  name5

示例结果

country | sports_team | number_of_players
c1      | teamA       | 2
c1      | teamB       | 1
c2      | teamC       | 2

我是编写SQL查询的新手，我不知道如何处理，任何帮助都将不胜感激！

Answer 1

使用GROUP BY：

SELECT country, sports_team, COUNT(*)
FROM whatever_your_table_is    
GROUP BY country, sports_team

Answer 2

试试这个：

SELECT country, sports_team, COUNT(*) AS number_of_players
FROM yourtable
GROUP BY country, sports_team
ORDER BY country, sports_team;

像COUNT这样的{p> Aggregate查询是此类数据处理的关键。

Answer 3

select 
  country,
  sports_team,
  count(*) number_of_players
from table
group by country, sports_team

Answer 4

试试这个：

SELECT 
  Country, Sports_Team, COUNT(player_name) AS number_of_players
FROM 
  YourTable
GROUP BY 
  Country, Sports_Team

Answer 5

select country, sports_team, count(*) from <your table> group by country, sports_team

Answer 6

无需循环，只需汇总。

SELECT country, sports_team, COUNT(*)
FROM myTable
GROUP BY country, sports_team

魔术在COUNT(*)和GROUP BY子句

中