delphi mysql query result - mysql

Question

for read data from database server im using mysql query like this:
FDQuery1.SQL.Text := 'select * from `table` WHERE dcid=3;';
FDQuery1.Open;
memo1.Lines.Add( FDQuery1.FieldByName('value').AsString );
but when i have to use a loop for read data from mysql
i need a array to read and store data on it
i know in php its like this
$arr = array();
while($obj = $q->fetch_object() ){
$arr[] = $obj;
}
but how can i do this syntax in Delphi ?

Answer 1

You don't need to do FDQuery1.First as that is implicit in the FDQuery1.Open. However if you want to know how many records you have it's important to do a FDQuery1.Last; before using FDQuery1.RecordCount to get the true record count otherwise you might get strange results.
All you need to do get your data into a memo is this
FDQuery1.SQL.Text := 'select * from table WHERE dcid=3;';
memo1.Lines.clear;
FDQuery1.Open;
While not FDQuery1.Eof do
begin
memo1.Lines.Add( FDQuery1.FieldByName('value').AsString );
FDQuery1.next;
end;
end;
FDQuery1.Close;
although a better solution with minimal exception handling is
FDQuery1.SQL.Text := 'select * from table WHERE dcid=3;';
memo1.Lines.clear;
try
try
begin
FDQuery1.Open;
While not FDQuery1.Eof do
begin
memo1.Lines.Add( FDQuery1.FieldByName('value').AsString );
FDQuery1.next;
end;
end;
end;
except
on E : Exception do
begin
showmessage ('Exception class name = '+E.ClassName+ slinebreak
+ 'Exception message = '+E.Message);
end //on E
end; //try-except
finally
FDQuery1.Close;
end; //try-finally
You mention an array. This is not needed if you only want to put the data in a memo but if you did want to put the data in an array (a dynamic array of variants as you don't know at design time how many record elements you need, how many field elements you need or what type each field is) then you would use the following code.
(Note this is deliberately not optimised code as I was trying to make the process clear)
Const
FirstRecordIndex = 0;
FirstFieldIndex = 0;
Var
DataArray : Variant;
TheRecordCount, TheFieldCount,
RecordNumber, FieldNumber : integer;
Data : variant;
begin
FDQuery1.SQL.Text := 'select * from table WHERE dcid=3;';
FDQuery1.Open;
FDQuery1.Last; //to get correct recordcount
TheRecordCount := FDQuery1.RecordCount;
TheFieldCount := FDQuery1.FieldCount;
FDQuery1.First; //go back to the beginning of the dataset
//set the dimensions of the 2D array of variants to hold data
DataArray := VarArrayCreate([FirstRecordIndex, TheRecordCount, FirstFieldIndex, TheFieldCount], varVariant ); //element can be of any type
//fill it
RecordNumber := -1; //initialise record indexe to just before the start
While not FDQuery1.Eof do
begin
inc(RecordNumber); //point to next record element in the array
for FieldNumber := FirstFieldIndex to TheFieldCount -1 do //load all the fields of this record
begin
Data := FDQuery1.Fields[FieldNumber].asVariant; //get the data
DataArray[RecordNumber, FieldNumber] := Data; //put into array
end;
FDQuery1.next; //get next record
end; //while
end;
FDQuery1.Close;
end;
To get the data back again use
For RecordNumber := FirstRecordIndex to TheRecordCount -1 do
For FieldNumber := FirstFieldIndex to TheFieldCount -1 do
begin
Data := DataArray[RecordNumber, FieldNumber] ;
//do something with the data ie put into a memo
end;

Answer 2

You can use this, i hope that help u:
FDQuery1.SQL.Text := 'select * from `table` WHERE dcid=3;';
FDQuery1.Open;
if FDQuery1.Active and (FDQuery1.RecordCount > 0) then
begin
FDQuery1.First;
While not FDQuery1.Eof do
begin
memo1.Lines.Add( FDQuery1.FieldByName('value').AsString );
FDQuery1.next;
end;
end;

Answer 3

you can do this with array of array consept
for this first you must create your new type
type
myArray = array [1..10] of integer;
myData= array of myArray;
and then you must define your variable
var
Records: myData;
i:integer;
on,now we have aarray of array to save database records on it so
begin
FDQuery1.SQL.Text := 'select * from table WHERE type=3;';
FDQuery1.Open;
FDQuery1.First;
SetLength(Records ,FDQuery1.recordcount);//or maybe you need a do a select count(*) query first
i:=0;
While not FDQuery1.Eof do
begin
Records[i][1]:= FDQuery1.FieldByName('value1').AsString;
Records[i][2]:= FDQuery1.FieldByName('value2').AsString;
Records[i][3]:= FDQuery1.FieldByName('value3').AsString;
Records[i][4]:= FDQuery1.FieldByName('value4').AsString;
Records[i][5]:= FDQuery1.FieldByName('value5').AsString;
Records[i][6]:= FDQuery1.FieldByName('value6').AsString;
i:=i+1;
FDQuery1.next;
end;
FDQuery1.Close;
end;
now all of your selected database records are in your local variable
you can go over the row and make new queries with FDQuery1...