Getting the size of a field.
lazarus / 16-Databases

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cov · 2013-05-15 21:06

I'm using Code:
[Select]fldSz:=SQLQuery1.FieldByName('FIELDNAME').Size; to get the
size of the field.

However, fldsz reports that the field size (as defined by the
VARCHAR(n) argument) is 11, yet opening the Table in Flame Robin
suggest that the field size is actually VARCHAR(6).

Is there any way of finding out what the field size is?

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howardpc · 2013-05-15 21:10

The apparent variation arises from ambiguity (or lack of clarity)
about the units of measurement. Do you want the size in characters or
bytes? And if in characters, what constitutes a character? And should
the field be large enough to accommodate strings in the least
compressed character encoding that might be encountered... or should
it set aside a fixed storage amount per anticipated character (say
two, or four bytes)? Does the size allow for string metadata (length,
BOM, encoding) or a trailing #0? Database implementations vary in
their anwers to these questions, and the defaults they assume.

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cov · 2013-05-15 21:17

I need the size of the field.

If it's defined as VARCHAR(6), then I would expectCode: [Select]
fldSz:=SQLQuery1.FieldByName(sfield).Size; to return '6'.

But if it returns '12', that's also okay, so long as I can ascertain
whether the value I'm about to insert will fit.

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cov · 2013-05-15 21:20

Sorry, the database I'm using is Firebrd.

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Lacak2 · 2013-05-16 05:54

You have only 2 options:
use TField.Size which should be CHARACTER length
and
TField.DataSize which should be BYTE length

But, correct results are returned only when used Single Bytes
Character Sets. When you start using MBCS (Unicode, UTF8 etc.) then
you must do your own "calculations" of size.

It is IMO not good situation and is awaiting for resolving.

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cov · 2013-05-16 10:14

Oops!

I was looking at the wrong table.

Code: [Select]fldSz:=SQLQuery1.FieldByName(sfield).Size; does indeed
return 6, if I specify the correct table!