如何在 SQL Server 2005/8 上获得类似表的查询结果？

Question

我有 3 张桌子：

users (id, name)

currency (id, name)

accounts (id, user_id, currency_id, amount)

我想从accounts 读取数据并将其呈现在类似表格的视图中：

owner  currency1 currency2 currency3
1      0         0         0
2     10        20        30
3      0         5        10

其中owner 是ID 中的accounts.owner、currency1,2,3 - (SELECT id FROM currency WHERE name = '1',etc)

我只能针对一个特定的 ID 获得这样的结果：

SELECT
  SELECT amount FROM accounts WHERE currency = (SELECT id FROM currency WHERE name = 'currency1') AND owner = @user) AS [currency1],
  SELECT amount FROM accounts WHERE currency = (SELECT id FROM currency WHERE name = 'currency2') AND owner = @user) AS [currency2],
  SELECT amount FROM accounts WHERE currency = (SELECT id FROM currency WHERE name = 'currency2') AND owner = @user) AS [currency2]

是否可以为users 表中的每个对象获得相同的结果？不使用报告服务等。

Answer 1

使用数据透视表和动态 SQL 检索列

    DECLARE @columns VARCHAR(2000)
    SELECT @columns = STUFF(( SELECT DISTINCT TOP 100 PERCENT
    '],[' + c.name
    FROM currency AS c
    ORDER BY '],[' + c.name
    FOR XML PATH('')
    ), 1, 2, '') + ']'

    DECLARE @query NVARCHAR(4000)
    SET @query = N'SELECT UserName, ' + @columns +
    'FROM 
    (SELECT u.Name AS UserName, c.name AS CurrencyName, a.Amount
    FROM Accounts AS a WITH(NOLOCK)
    JOIN Users u WITH(NOLOCK) ON a.user_id = u.user_id
    JOIN Currency c WITH(NOLOCK) ON a.currency_id = c.currency_id
    ) p
    PIVOT
    (
    SUM (p.Amount)
    FOR p.CurrencyName IN
    ( '+ @columns +')
    ) AS pvt
    ORDER BY UserName'

EXECUTE(@query)

这是在 SQL Server 2005 中测试的

Answer 2

听起来你想要一个数据透视表。如果您有不同数量的货币行，这将很难做到，但仍然可以通过使用动态编写的 sql 来完成。

下面是 MSDN 的资源，它解释了如何使用数据透视表：http://msdn.microsoft.com/en-us/library/ms177410.aspx

SELECT u.name, [1] AS Currency1, [2] AS Currency2, [3] AS Currency3
FROM 
(SELECT u.Name AS UserName, c.Currency_ID, a.Amount
FROM Accounts AS a WITH(NOLOCK)
JOIN Users u WITH(NOLOCK) ON a.user_id = u.user_id
) p
PIVOT
(
SUM (p.Amount)
FOR p.Currency_id IN
( [1], [2], [3] )
) AS pvt
ORDER BY pvt.UserName