多行的 where 子句，GROUP BY

Question

我有以下表结构

AccountID   Property            Value
123456      Status              Active
123456      City                Los Angeles
123456      RegistrationDate    2018-05-11 11:30:14.000
543210      Status              Active
543210      City                Las Vegas
543210      RegistrationDate    2018-05-11 11:13:14.000
888888      Status              Inactive
888888      City                Toronto
888888      RegistrationDate    2015-05-12 11:13:14.000 

我希望能够选择 Property == Status 和 Value == Active And Property == RegistrationDate and Value == 2018-05-11 11:30:14.000 的所有行

我想我需要做某种 GROUP BY 然后选择那个聚合，但我无法理解它（我的 sql 真的很生疏）。

我想要上面“查询”的以下输出

AccountID    Status    RegistrationDate
123456       Active    2018-05-11 11:30:14.000
543210       Active    2018-05-11 11:30:14.000

如果所有列都存在于同一行中，我会这样写：

SELECT AccountID FROM Property
WHERE Status = 'Active'
AND RegistrationDate = '2018-05-11 11:30:14.000'

Answer 1

该设计模式称为 EAV（实体-属性-值）。GROUP BY这种设计通常需要具有多个连接的 或 查询：

SELECT
      a.AccountID               
FROM 
      tbl AS a
      JOIN tbl AS b
      ON a.AccountID = b.AccountID
WHERE
      a.Property = 'Status' 
  AND a.Value    = 'Active'

  AND b.Property = 'RegistrationDate' 
  AND b.Value    = '2018-05-11 11:30:14.000' ;

Answer 2

另一种表达方式是使用PIVOT将 EAV 结构转换为表格形式。鉴于：

DROP TABLE IF EXISTS dbo.EAV;

CREATE TABLE dbo.EAV
(
    AccountID integer NOT NULL,
    Property varchar(30) NOT NULL,
    Value sql_variant NULL
);

INSERT dbo.EAV
    (AccountID, Property, [Value])
VALUES
    (123456, 'Status', CONVERT(sql_variant, 'Active')),
    (123456, 'City', CONVERT(sql_variant, 'Los Angeles')),
    (123456, 'RegistrationDate', CONVERT(sql_variant, CONVERT(datetime, '2018-05-11 11:30:14.000', 121))),
    (543210, 'Status', CONVERT(sql_variant, 'Active')),
    (543210, 'City', CONVERT(sql_variant, 'Las Vegas')),
    (543210, 'RegistrationDate', CONVERT(sql_variant, CONVERT(datetime, '2018-05-11 11:13:14.000', 121))),
    (888888, 'Status', CONVERT(sql_variant, 'Inactive')),
    (888888, 'City', CONVERT(sql_variant, 'Toronto')),
    (888888, 'RegistrationDate', CONVERT(sql_variant, CONVERT(datetime, '2015-05-12 11:13:14.000', 121)));

一个示例查询是：

SELECT
    P.AccountID,
    P.[Status],
    P.City,
    P.RegistrationDate
FROM dbo.EAV AS E
PIVOT (MAX([Value]) 
    FOR Property IN 
    (
        [Status], 
        [City], 
        [RegistrationDate])
    ) AS P
WHERE 
    P.[Status] = CONVERT(sql_variant, 'Active')
    AND P.RegistrationDate = CONVERT(sql_variant, CONVERT(datetime, '2018-05-11 11:30:14.000', 121));

结果：

帐号| 状态 | 城市 | 注册日期   
--------: | :----- | :---------- | :------------------
   123456 | 活跃 | 洛杉矶 | 11/05/2018 11:30:14

db<>在这里摆弄