如何解决在 SQL Server 2012 中,我可以使用 Rows Preceding 中的参数来计算动态移动平均线吗?
计算指定股票和天数的动态移动平均线的存储过程:
ALTER PROCEDURE sp_MovAvg
(@ticker NVARCHAR(6),@days INT)
AS
SELECT
@ticker AS Ticker,[Date],AVG ([px_Close]) OVER (ORDER BY @ticker,[Date]
ROWS BETWEEN @days PRECEDING AND CURRENT ROW) AS moving_avg
FROM
daily_data
WHERE
Ticker LIKE @ticker
ORDER BY
Ticker ASC,[Date] DESC
解决方法
不幸的是,ROWS BETWEEN
needs literals:
<window frame preceding> ::=
{
UNBOUNDED PRECEDING
| <unsigned_value_specification> PRECEDING
| CURRENT ROW
}
<unsigned value specification> ::=
{ <unsigned integer literal> }
您可以通过使用 LAG
和许多 CASE
表达式或自连接来解决此问题。
但最简单的可能是动态 SQL。
- 不要忘记参数化
@ticker
CREATE OR ALTER PROCEDURE MovAvg
(@ticker NVARCHAR(6),@days INT)
AS
DECLARE @sql nvarchar(max) = N'
SELECT
@ticker AS Ticker,[Date],AVG ([px_Close]) OVER (ORDER BY @ticker,[Date] -- Did you mean Ticker,[Date]??
ROWS BETWEEN ' + CAST(@days AS nvarchar(10)) + N' PRECEDING AND CURRENT ROW) AS moving_avg
FROM
daily_data
WHERE
Ticker LIKE @ticker
ORDER BY
Ticker ASC,[Date] DESC;
';
EXEC sp_executesql
@sql,N'@ticker NVARCHAR(6)',@ticker = @ticker;
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