Question

如果2个日期是硬编码的，则下面的查询有效，但是，我想用2个变量@FirstDayM和@LastDayM替换它们。当我这样做时，它会返回以下错误

＆＃34;从字符串＆＃34;

转换日期和/或时间时转换失败

DECLARE @sql varchar(max)
DECLARE @FirstDayM DATE = DATEADD(MONTH, DATEDIFF(MONTH, 0, GETDATE())-1, 0)
DECLARE @LastDayM DATE = DATEADD(MONTH, DATEDIFF(MONTH, -1, GETDATE())-1, -1);

    SELECT @sql = Coalesce(@sql + ' UNION ALL ', '') + 'SELECT COUNT(C1CustID) AS CertsCount, ''' + QuoteName(name)+  ''' as DBname FROM ' + QuoteName(name) + '.dbo.T_C1CustCourse'+
    ' WHERE C1CertificationDate_N >= '+'''2018-01-01'''+' AND C1CertificationDate_N <= '+'''2018-01-31'''
    FROM   sys.databases WHERE database_id > 4 AND state = 0;

EXEC (@sql);

Answer 1

使用sp_executesql。总是。它可以轻松地将参数放入查询中。即使动态查询不是以参数开头，您也可能决定稍后再添加一个。

declare @sql nvarchar(max);
declare @firstDayM date;
declare @lastDayM date;

set @firstDayM = ?;
set @lastDayM = ?;

SELECT @sql = Coalesce(@sql + ' UNION ALL ', '') + '
SELECT COUNT(C1CustID) AS CertsCount, ''' + QuoteName(name)+  ''' as 
DBname
FROM ' + QuoteName(name) + '.dbo.T_C1CustCourse' + '
WHERE C1CertificationDate_N >= @FirstDayM AND C1CertificationDate_N 
<= @LastDayM'
FROM sys.databases
WHERE database_id > 4 AND state = 0;

EXEC sp_executesql @sql, N'@FirstDayM date, @lastDayM date',
     @FirstDayM=@FirstDayM, @lastDayM=@lastDayM;

动态查询和使用变量

1 个答案: