基础问题,点拨一下

[sskset]

String sqlConnection = "Data Source=(local);Initial Catalog=northwind;User Id=sa;Password=keshan;";
String strSQL = " select * from customers where customerid like @input ";
SqlConnection conn = new SqlConnection(sqlConnection);
conn.Open();
SqlCommand cmd = new SqlCommand(strSQL,conn);
SqlParameter sp = new SqlParameter("@input",SqlDbType.VarChar,20);
sp.Value = this.textBox1.Text;
cmd.Parameters.Add(sp);

问题1:String strSQL = " select * from customers where customerid like @input ";
的话，如果 textBox1 的值是空 那么运行的时候就 没有数据，我想，如果textBox1 的值是空那么显示全部数据？以前做项目没有使用参数，想问的是如果使用参数的话大家平常是怎么处理的？

问题2:比如说this.textBox1.Text 的值为 aaa
怎么控制sql语句为 select * from customers where customerid like 'aaa%'?

[sskset]

明白了

[我不懂电脑]

问题1:只能根据textBox1 的值形成sql语句。

[zhanglizhao]

没明白楼主的意思

[epimetheus]

别那样写，如果Text文本框为空，就不要那个条件。如果不为空再要那个条件

[RedErick]

String strSQL = " select * from customers where 1=1";
if(this.textBox1.Text != "")
strSQL += " and customerid like '"+ this.textBox1.Text.Trim().Replace("'","''") +"'";

[xinbin1122]

if text=""
{
select * from customers

}
else
{
"select * from customers where customerid like '" + text.text + "'"
}
自己把格式补充完整

[wxwx110]

如果textBox1.Text为空那么将做无条件查询相当于
String strSQL = " select * from customers“



如果使用参数只需要对PARAMETERS里的对应的对象的VALUE值做一下字符串的处理就可以实现模糊查询了

[seekg]

tongshangshang

[dqjia]

like '%%'即显示所有记录

[9sun888]

楼主:

你不能把sp.Value = this.textBox1.Text;改成这一句:
sp.Value = this.textBox1.Text + "%";

[9sun888]

楼主:

改成sp.Value = this.textBox1.Text + "%";后,能同时满足你上面所提的2个要求!

[Ivony]

问题1:
sp.Value = this.textBox1.Text;
=>
sp.Value = this.textBox1.Text==""?"%":this.textBox1.Text;

问题2:
sp.Value = this.textBox1.Text+"%";

[zeusvenus]

先定义个变量字符串,把输入的字符赋予它,然后做个if判断按是否空来写不同的语句啊,有什么问题吗?

[silverseven7]

sp.Value = this.textBox1.Text;
=>
sp.Value = this.textBox1.Text==""?"%":this.textBox1.Text;

问题2:
sp.Value = this.textBox1.Text+"%";
sp.Value = this.textBox1.Text;
=>
sp.Value = this.textBox1.Text==""?"%":this.textBox1.Text;

问题2:
sp.Value = this.textBox1.Text+"%";
sp.Value = this.textBox1.Text;
=>
sp.Value = this.textBox1.Text==""?"%":this.textBox1.Text;

问题2:
sp.Value = this.textBox1.Text+"%";
sp.Value = this.textBox1.Text;
=>
sp.Value = this.textBox1.Text==""?"%":this.textBox1.Text;

问题2:
sp.Value = this.textBox1.Text+"%";