1、打开SQL Server Management Studio管理工具，连接上数据库，输入如下SQL语句创建一燹唉侗墉张测试表 CREATE TABLE [tblCountMax]( [Id] [varchar](40) NOT NULL, [Col1] [nvarchar](50) NULL, [Col2] [int] NULL, [Col3] [decimal](38,4) NULL CONSTRAINT [PK_ID] PRIMARY KEY CLUSTERED ( [Id] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] ) ON [PRIMARY]
3、查询表中现有的数据 select * from [tblCountMax];
5、使用count与where统计表中满足条件的记录行数 select count(1) from [tblCountMax] where ISNULL(Col2, '') <> '';
7、使用max(datalength(列))计算一个列的最大长度 select max(DATALENGTH(id)), max(DATALENGTH(Col1)) , max(DATALENGTH(Col2)), max(DATALENGTH(Col3)) from [tblCountMax]
