mysql - how to use Loop in c# insert query -


i'm student in vocational highschool , newbie programmer.. have problem using loop in insert query.. have 2 table, book , book_detail, wich link foreign key, , want save data both table, , problem every time add book, have textbox named copies_txt, idea want save same book_id , same location_id in book_detail table diffrent boookdetail_id as amount insert in copies_txt.. , achieve try using loop, gives me error

duplicate entry key primary

, here's full code

int copies = convert.toint32(copies_txt.text);                               int i;           string constring = "datasource=localhost;port=3306;username=root;password=root";         string query = "insert simbada_perpustakaan.book(book_id,title,release_date,genre,author,copies,create_by,create_date) values ('" + this.book_id.text + "','" + this.title_txt.text + "','" + this.time.text + "','" + this.genre_txt.text + "','" + this.author_txt.text + "','" + this.copies_txt.text + "','" + this.username_lbl.text + "','" + datetime.now.tostring("yyyy/mm/dd/hh/mm/ss") + "') ; ";         string query2 = "insert simbada_perpustakaan.book_detail(id_bookdetail,book_id,location_id) values('" + guid.newguid() + "','" + this.book_id.text + "','" + this.textbox1.text + "') on duplicate key update id_bookdetail=(id_bookdetail=('"+guid.newguid()+"'))";                     mysqlconnection condatabase = new mysqlconnection(constring);         mysqlcommand cmddatabase = new mysqlcommand(query, condatabase);         mysqlcommand cmddatabase2 = new mysqlcommand(query2, condatabase);         mysqldatareader myreader;         try         {             condatabase.open();             myreader = cmddatabase.executereader();             condatabase.close();                             (i = 0; <= copies; i++)             {                 condatabase.open();                 myreader = cmddatabase2.executereader();                 condatabase.close();                            }                           messagebox.show("saved");              while (myreader.read())             {              }         }         catch (exception ex)         {             messagebox.show(ex.message);         }

can please point out mistake... before.

i think issue second query. move query inside loop , check. don't need data reader since it's select statement. can avoid multiple database open , close statement. try below code

int copies = convert.toint32(copies_txt.text);                               int i;         string constring = "datasource=localhost;port=3306;username=root;password=root";         string query = "insert simbada_perpustakaan.book(book_id,title,release_date,genre,author,copies,create_by,create_date) values ('" + this.book_id.text + "','" + this.title_txt.text + "','" + this.time.text + "','" + this.genre_txt.text + "','" + this.author_txt.text + "','" + this.copies_txt.text + "','" + this.username_lbl.text + "','" + datetime.now.tostring("yyyy/mm/dd/hh/mm/ss") + "') ; ";          mysqlconnection condatabase = new mysqlconnection(constring);         mysqlcommand cmddatabase = new mysqlcommand(query, condatabase);          mysqldatareader myreader;         try         {             condatabase.open();            cmddatabase.executenonquery();              (i = 0; <= copies; i++)             {                string = guid.newguid().tostring();               string query2 = "insert simbada_perpustakaan.book_detail(id_bookdetail,book_id,location_id) values('" + + "','" + this.book_id.text + "','" + this.textbox1.text + "') on duplicate key update id_bookdetail=(id_bookdetail=('"+a+"'))";                 mysqlcommand cmddatabase2 = new mysqlcommand(query2, condatabase);                cmddatabase2.executenonquery();               }                           messagebox.show("saved");              condatabase.close();         }         catch (exception ex)         {             messagebox.show(ex.message);         }

also try parameterized query. can avoid sql injection problem.


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