如何执行ALTER TABLE查询？

Question

I have an SQL table called tbl, im trying to add the columns A, B and C to it.

When i execute the command :

String addcolumns = "ALTER TABLE SqlCreatedTbl ADD  A char(50) ;";
                        ......
             cmd = new SqlCommand(addcolumns, conn);
             conn.Open();
             cmd.ExecuteNonQuery();

The column is added !

However, when i try to add multiple columns, it does NOT work, it gives me an error.. the command im writting for adding multiple columns is the following:

addcolumns = "ALTER TABLE SqlCreatedTbl ADD  ( A char(50),  B char(50), C char(50) );";

the debugger highlights the line : cmd.ExecuteNonQuery(); and throws the following exception:

Exception Details: System.Data.SqlClient.SqlException: Incorrect syntax near '('.

Answer 1

Get rid of the parentheses you've added in the ADD clause. You don't have them in the single column version, and you don't need them with multiple columns either. Specify ADD once and then just comma-separate your list

Answer 2

如果要与SQL Server数据库进行交互（使用T-SQL），则即使添加多个列，也不能在列定义列表的周围加上括号：

ALTER TABLE SqlCreatedTbl ADD A char(50), B char(50), C char(50);