Why is Delphi (Zeos) giving me widestring fields in SQLite when I ask for unsigned big int?

Question

I am using the latest Zeos with SQLite 3. It is generally going well, converting from MySQL, once we made all the persistent integer field TLargeInt.

Bu

Answer 1

Zeos uses the following code (in ZDbcSqLiteUtils.pas) to determine a column's type:

Result := stString;
...
if StartsWith(TypeName, 'BOOL') then
  Result := stBoolean
else if TypeName = 'TINYINT' then
  Result := stShort
else if TypeName = 'SMALLINT' then
  Result := stShort
else if TypeName = 'MEDIUMINT' then
  Result := stInteger
else if TypeName = {$IFDEF UNICODE}RawByteString{$ENDIF}('INTEGER') then
  Result := stLong //http://www.sqlite.org/autoinc.html
else if StartsWith(TypeName, {$IFDEF UNICODE}RawByteString{$ENDIF}('INT')) then
  Result := stInteger
else if TypeName = 'BIGINT' then
  Result := stLong
else if StartsWith(TypeName, 'REAL') then
  Result := stDouble
else if StartsWith(TypeName, 'FLOAT') then
  Result := stDouble
else if (TypeName = 'NUMERIC') or (TypeName = 'DECIMAL')
  or (TypeName = 'NUMBER') then
begin
 { if Decimals = 0 then
    Result := stInteger
  else} Result := stDouble;
end
else if StartsWith(TypeName, 'DOUB') then
  Result := stDouble
else if TypeName = 'MONEY' then
  Result := stBigDecimal
else if StartsWith(TypeName, 'CHAR') then
  Result := stString
else if TypeName = 'VARCHAR' then
  Result := stString
else if TypeName = 'VARBINARY' then
  Result := stBytes
else if TypeName = 'BINARY' then
  Result := stBytes
else if TypeName = 'DATE' then
  Result := stDate
else if TypeName = 'TIME' then
  Result := stTime
else if TypeName = 'TIMESTAMP' then
  Result := stTimestamp
else if TypeName = 'DATETIME' then
  Result := stTimestamp
else if Pos('BLOB', TypeName) > 0 then
  Result := stBinaryStream
else if Pos('CLOB', TypeName) > 0 then
  Result := stAsciiStream
else if Pos('TEXT', TypeName) > 0 then
  Result := stAsciiStream;

If your table uses any other type name, or if the SELECT output column is not a table column, then Zeos falls back to stString. There's nothing you can do about that; you'd have to read the values from the string field (and hope that the conversion to string and back does not lose any information).

It might be a better idea to use some other library that does not assume that every database has fixed column types.