[英]Get text[] value from sql table with FireDAC on Delphi
On pgAdmin with a simple query 'select * from data' I got only one record containing a field type text[] with value '{"1","2","3"}'. 在带有简单查询'select * from data'的pgAdmin上,我只得到一条包含字段类型text []的记录,其值为'{“1”,“2”,“3”}'。 The following simplified code gives back only the "1" part of the value:
以下简化代码仅返回值的“1”部分:
function GetData: string;
var
q: TFDQuery;
s: string;
i: integer;
av: array of variant;
as: array of string;
begin
result:='';
q:=TFDQuery.Create(nil);
try
q.Connection:=FDConnection;
q.SQL.Text:='select * from data';
try
q.Open;
while not q.Eof do
begin
//s:=q.FieldByName('data_array').AsString; //s = '1'
//as:=q.FieldByName('data_array').AsVariant; //as length = 1; as[0] = '1'
av:=q.FieldByName('data_array').AsVariant;
for i:=0 to Length(av)-1 do s:=s+av[i]; //av length = 1; s = '1'
q.Next;
end;
result:=q.RecordCount;
except
result:=-2;
end;
finally
q.Free;
sl.Free;
end;
end;
What is the way to get the whole data? 获取整个数据的方法是什么?
Although Embarcadero documentation says you should use TArrayField casting (It works for Interbase): 虽然Embarcadero文档说你应该使用TArrayField cast(它适用于Interbase):
procedure TFrmMain.Button1Click(Sender: TObject);
var
F: TArrayField;
V: Variant;
begin
F := TArrayField(q.FieldByName('data_array'));
V := F.FieldValues[0];
ShowMessage(VarToStr(V));
end;
It seem not to work correctly for PostgreSQL ( at least with C++ builder XE6 i am getting only first array item). 它似乎不适用于PostgreSQL(至少对于C ++构建器XE6我只得到第一个数组项)。 Firedac handles PostgreSQL array fields as nested datasets, therefore if above doesn't work for you as well, in C++ you might use PG array as ordinary DataSet, accessing items by moving cursor eg :
Firedac将PostgreSQL数组字段作为嵌套数据集处理,因此如果上述内容对您不起作用,则在C ++中您可以将PG数组用作普通DataSet,通过移动游标来访问项目,例如:
TDataSetField * TT = (TDataSetField*)q->FieldByName("data_array");
TT->NestedDataSet->RecNo=2; // or while(!q->NestedDataSet->eof) etc.
ShowMessage(TT->NestedDataSet->Fields->Fields[0]->AsString);
wchich translated to delphi in your case would look like ( may be misspelled): 在您的情况下翻译为delphi的wchich看起来像(可能拼写错误):
...
var
TT: TDataSetField;
...
begin
TT:= TDataSetField(q.FieldByName('data_array'));
while not TT.NestedDataSet.Eof do
begin
s:= s+ TT.NestedDataSet.Fields.Fields[0].AsString; //0 - only single dimension supported
TT.NestedDataSet.Next;
end;
end;
Kind regards 亲切的问候
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