Question

出于某种原因，我无法在此处获得正确的语法来添加OPTION

   Database db = DatabaseFactory.CreateDatabase(Config.DbConnectionString);

    using (DbCommand cmd = db.GetSqlStringCommand(string.Format(@"  SELECT  t.customerID,
                                                                            t.Photo
                                                                    FROM SomeTable t
                                                                    WHERE t.PhotoID = (SELECT MAX(PhotoID) FROM SomeTable WHERE customerID = @{0} OPTION (OPTIMIZE FOR UNKNOWN)
                                                                    GROUP BY CustomerID ) ", "customerID")))
    {
        try
        {
            db.AddInParameter(cmd, "@customerID", DbType.String, customerID);

Answer 1

您在子查询之后，在分组之前放置了提示。

看起来应该是这样的：

SELECT t.customerID,
       t.Photo
FROM SomeTable t
WHERE t.PhotoID = (
                     SELECT MAX(PhotoID) 
                     FROM SomeTable 
                     WHERE customerID = @{0}
                  )
GROUP BY CustomerID
OPTION (OPTIMIZE FOR UNKNOWN)

您的混淆可能是由于提示与参数值有关，因此您认为必须将其放在参数之后。但OPTION 总是引入了query hint。也许，牢记这一点将有助于您记住正确的语法，即OPTION应该始终在整个查询的末尾。

无法将OPTION添加到T-SQL查询语法

1 个答案: