Question

我是PIVOT函数的新手，到目前为止，在旋转表时我无法成功运行任何查询。

这是数据源：

region         countries
Africa         180
Antarctica     3
Asia           99
Europe         154
Middle East    54
North America  123
Oceania        87
South America  48

我需要每个区域都变成一列-仅包含该区域中国家/地区的一行。

兼容性级别：SQL Server 2019（150）

我尝试了所有可以在网上找到的建议，但仍然不明白我在做什么错。

SELECT [Africa], [Asia], [Middle East], [North America], 
       [Oceania], [South America], [Antarctica]
FROM (
  SELECT region, count(name) as countries
  FROM dbo.country
  Group by region
) AS pDataSource
PIVOT
(
 countries
    FOR region IN ([Africa], [Asia], [Middle East], [North America], 
    [Oceania], [South America], [Antarctica])
) AS pPivotTable

第156条消息，第15级，状态1，第10行
关键字“ FOR”附近的语法不正确。

Answer 1

您缺少聚合通知sum(countries)

...
PIVOT
(
 sum(countries) 
    FOR region IN ([Africa], [Asia], [Middle East], [North America], 
    [Oceania], [South America], [Antarctica])
) AS pPivotTable

Answer 2

为什么不只使用条件聚合？

const isUnknownRecord = (u: unknown): u is Record<string, unknown> =>
  typeof u === 'object' && u !== null

export function serialize(data: unknown): string {
  if (data === null) {
    return ''
  }

  if (isUnknownRecord(data)) {
    let serializedData = ''
    for (const k of Object.keys(data).sort()) {
      serializedData += k
      if (data[k] !== null) {
        serializedData += serialize(data[k])
      }
    }
    return serializedData
  }

  return String(data)
}

如何解决错误：关键字'FOR'

2 个答案: