Firstly, you should not use keywords
] like 'table' for a table name.
Secondly, it looks like there is no space after tablename.
SqlCommand cm = new SqlCommand("insert into myTable (name,num,sal,phone) values('" + textBox1.Text + "'," + textBox2.Text + "," + textBox3.Text + "," + textBox4.Text + ")", con);
Third thing, it's bad practice to pass on the controls value directly in query. This can lead to SQL Injection. Read about protecting from SQL Injection here: SQL Injection Mitigation: Using Parameterized Queries