多条件查询sql语句

查询时根据你所输入的内容进行查询

str_query1 = "select * from table";
                string key1 = "";
                string key2 = "";
                string key3 = "";
                string key4 = "";    //有几个条件就加几个key,我这里有四个
        
                if (textBox1.Text.Trim() != "")
                    key1 = " column1 like '%" + textBox1.Text.Trim() + "%'";

                if (textBox2.Text.Trim() != "")
                    key2 = " column2 like '%" + textBox2.Text.Trim() + "%'";

                if (textBox3.Text.Trim() != "")
                    key3 = " column3 like '%" + textBox3.Text.Trim() + "%'";
 
                if (textBox4.Text.Trim() != "")
                    key4 = " column4 like '%" + textBox4.Text.Trim() + "%'"; //这也一样

    

                if (key1 != "" || key2 != "" || key3 != "" || key4 != "" )
                {
                    str_query1 = "select * from table where";
                    if (key1 != "")                                        //这些条件是个递增的过程，有几个条件就加几个if语句
                    {
                        str_query1 += key1;
                    }

                    if (key1 != "" && key2 != "")
                    {
                        str_query1 += "and" + key2;
                    }
                    else
                    {
                        str_query1 += key2;
                    }

 else
                    {
                        str_query1 += key2;
                    }

                    if ((key1 != "" || key2 != "") && key3 != "")
                    {
                        str_query1 += "and" + key3;
                    }
                    else
                    {
                        str_query1 += key3;
                    }

                    if ((key1 != "" || key2 != "" || key3 != "") && key4 != "")     //后面还可以加key5,相信你看到这里已经名白怎么加了
                    {
                        str_query1 += "and" + key4;
                    }
                    else
                    {
                        str_query1 += key4;
                    }
}