{“操作符类型冲突：int与文本不兼容”}

Question

Whenever I run this query I get this error. Help is appreciated.

{"Operand type clash: int is incompatible with text"}

this is my code:

SqlCommand cmd1 = cons.CreateCommand();
                cmd1.CommandType = CommandType.Text;
                cmd1.CommandText = "update coffeeshop set Quantity=convert(varchar(MAX),Quantity)-" + t1.Text;

                cmd1.ExecuteNonQuery();

If I take away the convert(varchar(Max) as it can be seen in code bellow:

 SqlCommand cmd1 = cons.CreateCommand();
        cmd1.CommandType = CommandType.Text;
        cmd1.CommandText = "update coffeeshop set Quantity=Quantity-" + t1.Text;
        cmd1.ExecuteNonQuery();

Then I get this error:

{"Operand type clash: text is incompatible with int"}

Answer 1

Try this out assuming quantity is varchar :

cmd1.CommandText = "update coffeeshop set Quantity= Convert(int,Quantity)-" + t1.Text;

for text try this:

cmd1.CommandText = "update coffeeshop set quantity= Convert(varchar(max) , Convert(INT, Convert(varchar(max),quantity))- "+ t1.Text + ")";