MyDAC and TMyQuery

Ithilien · Post by **Ithilien** » Tue 27 Feb 2007 22:05

Hello,

i'm very noob using MyDac and MySQL. I'm trying to make a Query in C++ Builder. My code is the following:( trying to do one )

MyConsulta->Connection = MyConnection;
MyConsulta->SQL->Add("SELECT * FROM user");
MyConsulta->Active = true;

But now, i don´t know if the result of the query is on MyConsulta object, or i must asignate to an other object ( intuitiveli: vector ( of users ) = MyQuery->Execute() ).

If someone can help me i would be very pleased.

Thanks a lot!!

Antaeus · Post by **Antaeus** » Thu 01 Mar 2007 08:55

As a rule you should not assign query execution result to anything. After you open a query, you can access retrieved data using, for example, the FieldByName property. This may look like this:

Code: Select all

 
  s = MyConsulta->FieldByName("string field")->AsString;    // s is a string variable
  n = MyConsulta->FieldByName("integer field")->AsInteger;  // n is an integer variable

Use MyConsulta->Next to scroll to the next record. For more information about using DataSets, read the Delphi Help documentation.

Ithilien · Post by **Ithilien** » Thu 01 Mar 2007 09:59

That's right!!!!!

Thanks a lot, but now i have a new problem. I have a field having a photograph ( picture ) from the user. I created it using longblob, but now, i dont know how can i retrieve from the BD. Neither i know how to insert into BD using C++ Builder.

Can you explain me? And can you put an example to guide? I know that there are TImage Object, but if i use FieldByName, AsImage?? ( exists? )

Thanks

Antaeus · Post by **Antaeus** » Fri 02 Mar 2007 12:26

Please refer to this thread. Here you will find some examples on how to work with the BLOB fields in C++Builder.

Ithilien · Post by **Ithilien** » Sat 10 Mar 2007 17:44

I can't do this:

i have to select a file ( jpg ) and i convert it to bmp without problems, but...i have to store it to DB. The SQL sentence i don't know how to do it.

My code is:

Code: Select all


insercion = "INSERT INTO planta (id_planta) VALUES("+ id + ")";
                                MyTablaPlanta->SQL->Clear();
                                MyTablaPlanta->SQL->Add(insercion);
                                MyTablaPlanta->ParamByName("blob")->LoadFromFile("C:\temp.bmp",ftBlob);
                                MyTablaPlanta->Execute();

But it doesn't work. Neither using MyTablaPlantaplano->LoadFromFile("C:\temp.bmp"); ( field called plano --> image )
MyTablaPlanta->Post();

Somebody help me?

Ithilien · Post by **Ithilien** » Sat 10 Mar 2007 17:45

I can't do this:

i have to select a file ( jpg ) and i convert it to bmp without problems, but...i have to store it to DB. The SQL sentence i don't know how to do it.

My code is:

Code: Select all


insercion = "INSERT INTO planta (id_planta) VALUES("+ id + ",:blob)";
                                MyTablaPlanta->SQL->Clear();
                                MyTablaPlanta->SQL->Add(insercion);
                                MyTablaPlanta->ParamByName("blob")->LoadFromFile("C:\temp.bmp",ftBlob);
                                MyTablaPlanta->Execute();

But it doesn't work. Neither using MyTablaPlantaplano->LoadFromFile("C:\temp.bmp"); ( field called plano --> image )
MyTablaPlanta->Post();

Somebody help me?

This code was rigth, but doesn't work

Antaeus · Post by **Antaeus** » Mon 12 Mar 2007 07:50

The code in your last post looks incorrect. You missed a BLOB field name in the INSERT statement. Only the id_planta field name appears. Please change your code and try again.
If this still does not work, please post the exact error message you get.

Ithilien · Post by **Ithilien** » Mon 12 Mar 2007 19:01

Yeah but, it doesn't work again.

I resolved problem:

"insercion" is an AnsiString variable. I tryed to insert from a a temp file created in bmp format doing that statement:

Code: Select all

 insercion = insert into planta values("+id+",LOAD_FILE(C:\temp.bmp)"

;

But my application didn't insert the row. So, exploring the variable i saw that it was a conversion of the text because character \ is special. So i put C:\temp.bmp and the insert statement was quite successfully.

At this point, one more problem appeared: Maps ( .bmp ) so big cant insert into DB. So the enviroment variable max_allowed_packet must be modified.

Code: Select all

 mysql> set max_allowed_packet = 1600000000

( the value 1600000000 for example for me was enough ).

Now i can insert doing those two command. NO PROBLEMS NOW!!!

Regards![/code]