编写sql查询的帮助

我正在尝试编写一个查询，以获取表中每个国家的运动队球员人数：

我有一个包含以下字段的表

country | sports_team | player_name

我想展示的是一个与此类似的reulst

country | sports_team | number_of_players

i、 我想环游所有国家，对于运动队的每一次变化，我想记录下队中球员的数量

样本表：

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

样本结果

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

我刚开始编写sql查询，我不知道如何处理，如果有任何帮助，我将不胜感激

使用：

使用：

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;

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

像COUNT这样的查询是此类数据处理的关键。

尝试以下方法：

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

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

像COUNT这样的查询是此类数据处理的关键。

尝试以下方法：

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

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

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;

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

---

不需要循环，只需聚合

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

---

神奇之处在于COUNT*和groupby子句不需要循环，只需聚合即可

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

---

神奇之处在于COUNT*和GROUPBY子句

尝试在SELECT语句中读取少量内容。这应该在第2页左右。试着在SELECT语句上读少量内容。这应该在第2页。