mySQL：按大小写、分组和排序

我有一个简单的表格，在这里我存储了一堆股票的市值。我正在尝试创建一个查询，该查询将返回以下内容：

cap_type  type_count
micro     4
small     6
large     1
mega      2

我不知道如何调整此查询以计算不同select案例组中cap_类型的数量。以下是我目前掌握的情况：

SELECT CASE
    WHEN market_cap < 10 THEN 'micro' 
    WHEN market_cap >= 10 < 50 THEN 'small' 
    WHEN market_cap >= 50 < 100 THEN 'large' 
    ELSE 'mega' 
END AS cap_type
FROM stocks
GROUP BY CASE
    WHEN market_cap < 10 THEN 'micro' 
    WHEN market_cap >= 10 < 50 THEN 'small' 
    WHEN market_cap >= 50 < 100 THEN 'large' 
    ELSE 'mega' 
    END
ORDER BY cap_type ASC

您可以使用子查询：

SELECT sub.cap_type, COUNT(*) AS type_count
FROM (
    SELECT CASE WHEN market_cap < 10 THEN 'micro' 
                WHEN market_cap < 50 THEN 'small' 
                WHEN market_cap < 100 THEN 'large' 
                ELSE 'mega' 
           END AS cap_type
    FROM temp
) AS sub  
GROUP BY sub.cap_type
ORDER BY 
CASE sub.cap_type
  WHEN 'micro' THEN 1
  WHEN 'small' THEN 2
  WHEN 'large' THEN 3
  ELSE 4
END;

---

如果您需要所有组，您可以使用子查询列出它们，然后

左键联接

：

SELECT sub.cap_type, COUNT(t.market_cap) AS type_count
FROM (SELECT 'micro' AS cap_type
      UNION ALL SELECT 'small'
      UNION ALL SELECT 'large' 
      UNION ALL SELECT 'mega') AS sub
LEFT JOIN temp t
  ON CASE
    WHEN t.market_cap < 10 THEN 'micro' 
    WHEN t.market_cap < 50 THEN 'small' 
    WHEN t.market_cap < 100 THEN 'large' 
    ELSE 'mega' 
    END = sub.cap_type
GROUP BY sub.cap_type
ORDER BY 
  CASE cap_type
    WHEN 'micro' THEN 1
    WHEN 'small' THEN 2
    WHEN 'large' THEN 3
    ELSE 4
  END

---

你试过以下方法吗？还是我理解错了问题

SELECT 
  CASE
    WHEN market_cap < 10 THEN 'micro' 
    WHEN market_cap >= 10 < 50 THEN 'small' 
    WHEN market_cap >= 50 < 100 THEN 'large' 
    ELSE 'mega' 
  END AS cap_type,
  COUNT(*) as count
FROM stocks
GROUP BY cap_type
ORDER BY cap_type ASC;

选择
案例
当市值小于10时，则为“微型”
当市值>=10<50时，则为“小”
当市值>=50<100时，则为“大”
其他“巨型”
端部为cap_类型，
计数（*）作为计数
库存
按cap_类型分组
按cap_类型ASC订购；

UPD：您的案例语句包含细微错误（您遗漏了和，并且条件没有意义，尽管形式上是正确的），下面是正确的查询（当条件停止处理时匹配）：

选择
案例
当市值小于10时，则为“微型”
当市值小于50时，则为“小”
当市值<100时，则为“大”
其他“巨型”
端部为cap_类型，
计数（*）作为计数
库存
按cap_类型分组
按cap_类型ASC订购；

选择
案例
当市值小于10时，则为“微型”
当市值>=10且市值<50时，则为“小”
当市值>=50且市值<100时，则为“大”
其他“巨型”
端部为cap_类型，
计数（*）
现货
分组
当市值小于10时，则为“微型”
当市值>=10且市值<50时，则为“小”
当市值>=50且市值<100时，则为“大”
其他“巨型”
结束
按cap_类型ASC订购；

---

这成功了，谢谢！现在我看看SQL，我可以确切地看到CASE语句在做什么，以及如何/在哪里调用其他字段。@Gunnar，顺便说一句，我复制并粘贴了您的CASE语句，它包含错误，我更新了正确解决方案的答案。

SELECT sub.cap_type, COUNT(t.market_cap) AS type_count
FROM (SELECT 'micro' AS cap_type
      UNION ALL SELECT 'small'
      UNION ALL SELECT 'large' 
      UNION ALL SELECT 'mega') AS sub
LEFT JOIN temp t
  ON CASE
    WHEN t.market_cap < 10 THEN 'micro' 
    WHEN t.market_cap < 50 THEN 'small' 
    WHEN t.market_cap < 100 THEN 'large' 
    ELSE 'mega' 
    END = sub.cap_type
GROUP BY sub.cap_type
ORDER BY 
  CASE cap_type
    WHEN 'micro' THEN 1
    WHEN 'small' THEN 2
    WHEN 'large' THEN 3
    ELSE 4
  END

╔═══════════╦════════════╗
║ cap_type  ║ type_count ║
╠═══════════╬════════════╣
║ micro     ║          1 ║
║ small     ║          1 ║
║ large     ║          2 ║
║ mega      ║          0 ║
╚═══════════╩════════════╝   

SELECT 
  CASE
    WHEN market_cap < 10 THEN 'micro' 
    WHEN market_cap >= 10 < 50 THEN 'small' 
    WHEN market_cap >= 50 < 100 THEN 'large' 
    ELSE 'mega' 
  END AS cap_type,
  COUNT(*) as count
FROM stocks
GROUP BY cap_type
ORDER BY cap_type ASC;

SELECT 
  CASE
    WHEN market_cap < 10 THEN 'micro' 
    WHEN market_cap < 50 THEN 'small' 
    WHEN market_cap < 100 THEN 'large' 
    ELSE 'mega' 
  END AS cap_type,
  COUNT(*) as count
FROM stocks
GROUP BY cap_type
ORDER BY cap_type ASC;

SELECT 
CASE
    WHEN market_cap < 10 THEN 'micro'
    WHEN market_cap >= 10 and market_cap < 50 THEN 'small'
    WHEN market_cap >= 50 and market_cap < 100 THEN 'large'
    ELSE 'mega'
END AS cap_type,
count(*)
FROM stock
GROUP BY CASE
    WHEN market_cap < 10 THEN 'micro'
    WHEN market_cap >= 10 and market_cap < 50 THEN 'small'
    WHEN market_cap >= 50 and market_cap < 100 THEN 'large'
    ELSE 'mega'
END
ORDER BY cap_type ASC;