SQL Server的一些小技巧

·假设admin_comments是ntext类型，不能直接用另外的ntext来赋值。可以用转换到nvarchar(8000)来过渡。例如：
UPDATE meta SET admin_comments = (SELECT TOP 1 CAST(admin_comments As varchar(8000)) FROM meta WHERE reference_code = @reference_code ORDER BY lastUpdate)
    WHERE meta_id = @id


·察看纪录有没有重复，如果重复打印出重复的纪录个数：
SELECT     [col], COUNT [col] AS Expr1
FROM         [table]
GROUP BY [col]
HAVING      (COUNT([col]) > 1)