MySQL：大小写,组和排序依据

我有一个简单的表格,用于存储一堆股票的市值.我正在尝试查看是否可以创建将返回如下内容的查询：

cap_type  type_count
micro     4
small     6
large     1
mega      2

我不确定如何调整此查询以计算不同选择案例组中的cap_types数量.这是我到目前为止的内容：

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

以下是一些示例数据：

CREATE TABLE `stocks` (
  `id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `stock` varchar(4) COLLATE utf8_unicode_ci DEFAULT NULL,
  `market_cap` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`)
)
INSERT INTO temp (`stock`,`market_cap`) VALUES ('MSFT', 40);
INSERT INTO temp (`stock`,`market_cap`) VALUES ('MINI', 4);
INSERT INTO temp (`stock`,`market_cap`) VALUES ('GOOG', 50);
INSERT INTO temp (`stock`,`market_cap`) VALUES ('F', 90);

解决方法:

您是否尝试过以下方法？还是我理解问题错了？

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;

UPD：您的CASE语句包含细微的错误(虽然在形式上正确,但您错过了AND,并且条件没有意义,尽管在形式上正确),这是正确的查询(匹配的WHEN条件会停止处理)：

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;

标签：case,sql-order-by,mysql,group-by
来源： https://codeday.me/bug/20191119/2034728.html