用于分组的SQL Server查询

我有一个表，有两列

plateno

和

alerts

表

数据

plateno    alerts
  A         1
  B         2
  C         2
  A         3
  B         2
  A         4
  A         1

现在我想得到这样的结果：

alerts->   1  2  3  4
---------------------------
A          2  0  1  1
B          0  2  0  0
C          0  1  0  0

我的意思是“A”有两个类型为“1”的警报，一个类型为“3”和“4”的警报……以此类推

这是我正在尝试的问题

Select count(alert) 
from mytable 
group by plateno

试试这个：

SELECT plateno
,SUM(CASE alerts WHEN 1 THEN 1 ELSE 0 END) AS [1]
,SUM(CASE alerts WHEN 2 THEN 1 ELSE 0 END) AS [2]
,SUM(CASE alerts WHEN 3 THEN 1 ELSE 0 END) AS [3]
,SUM(CASE alerts WHEN 4 THEN 1 ELSE 0 END) AS [4]
FROM Table1
GROUP BY plateno

输出：

╔═════════╦═══╦═══╦═══╦═══╗
║ PLATENO ║ 1 ║ 2 ║ 3 ║ 4 ║
╠═════════╬═══╬═══╬═══╬═══╣
║ A       ║ 2 ║ 0 ║ 1 ║ 1 ║
║ B       ║ 0 ║ 2 ║ 0 ║ 0 ║
║ C       ║ 0 ║ 1 ║ 0 ║ 0 ║
╚═════════╩═══╩═══╩═══╩═══╝

╔═════════╦═══╦═══╦═══╦═══╗
║ PLATENO ║ 1 ║ 2 ║ 3 ║ 4 ║
╠═════════╬═══╬═══╬═══╬═══╣
║ A       ║ 2 ║ 0 ║ 1 ║ 1 ║
║ B       ║ 0 ║ 2 ║ 0 ║ 0 ║
║ C       ║ 0 ║ 1 ║ 0 ║ 0 ║
╚═════════╩═══╩═══╩═══╩═══╝

试试这个：

SELECT plateno
,SUM(CASE alerts WHEN 1 THEN 1 ELSE 0 END) AS [1]
,SUM(CASE alerts WHEN 2 THEN 1 ELSE 0 END) AS [2]
,SUM(CASE alerts WHEN 3 THEN 1 ELSE 0 END) AS [3]
,SUM(CASE alerts WHEN 4 THEN 1 ELSE 0 END) AS [4]
FROM Table1
GROUP BY plateno

输出：

╔═════════╦═══╦═══╦═══╦═══╗
║ PLATENO ║ 1 ║ 2 ║ 3 ║ 4 ║
╠═════════╬═══╬═══╬═══╬═══╣
║ A       ║ 2 ║ 0 ║ 1 ║ 1 ║
║ B       ║ 0 ║ 2 ║ 0 ║ 0 ║
║ C       ║ 0 ║ 1 ║ 0 ║ 0 ║
╚═════════╩═══╩═══╩═══╩═══╝

╔═════════╦═══╦═══╦═══╦═══╗
║ PLATENO ║ 1 ║ 2 ║ 3 ║ 4 ║
╠═════════╬═══╬═══╬═══╬═══╣
║ A       ║ 2 ║ 0 ║ 1 ║ 1 ║
║ B       ║ 0 ║ 2 ║ 0 ║ 0 ║
║ C       ║ 0 ║ 1 ║ 0 ║ 0 ║
╚═════════╩═══╩═══╩═══╩═══╝

试试这个：-

Select plateno,[1],[2],[3],[4]
from 
(
 Select plateno,alerts from Sample
)p
pivot 
(
 count(alerts)
 for alerts in ([1],[2],[3],[4])
)pvt

演示
试试这个：-

Select plateno,[1],[2],[3],[4]
from 
(
 Select plateno,alerts from Sample
)p
pivot 
(
 count(alerts)
 for alerts in ([1],[2],[3],[4])
)pvt

演示
如果列
警报

的值数目未知，则更倾向于使用动态sql

DECLARE @colList AS NVARCHAR(MAX), @sqlStatement AS NVARCHAR(MAX)

SELECT @colList = STUFF((SELECT DISTINCT ',' + QUOTENAME(alerts) 
                    FROM data
            FOR XML PATH(''), TYPE
            ).value('.', 'NVARCHAR(MAX)') ,1,1,'')


SET @sqlStatement = 'SELECT plateno,' + @colList + ' 
             FROM 
             (
                SELECT plateno, alerts 
                FROM data
             ) dta
             pivot 
             (
                COUNT(alerts)
                FOR alerts IN (' + @colList + ')
             ) pvt '

EXECUTE(@sqlStatement)

输出

---

如果列

Alert

的值数目未知，则更倾向于使用动态sql

DECLARE @colList AS NVARCHAR(MAX), @sqlStatement AS NVARCHAR(MAX)

SELECT @colList = STUFF((SELECT DISTINCT ',' + QUOTENAME(alerts) 
                    FROM data
            FOR XML PATH(''), TYPE
            ).value('.', 'NVARCHAR(MAX)') ,1,1,'')


SET @sqlStatement = 'SELECT plateno,' + @colList + ' 
             FROM 
             (
                SELECT plateno, alerts 
                FROM data
             ) dta
             pivot 
             (
                COUNT(alerts)
                FOR alerts IN (' + @colList + ')
             ) pvt '

EXECUTE(@sqlStatement)

输出

SQL fiddle

---

SQL fiddle

您尝试使用的SQL查询在哪里？您尝试使用的SQL查询在哪里？