use tstream datatype, tblobfield(fieldname).savetostream(); then judge stream's size
简单 if table1.fieldbyname('fieldname').isnull then //为空
Indicates whether the BLOB field contains any data.property IsNull: Boolean;DescriptionRead IsNull to determine whether the BLOB field is blank. IsNull is True if the BLOB field is empty. IsNull is False if the BLOB field contains any data.if Query1Images.IsNull then ShowMessage('You forgot the BLOB data!');
tblobfield(fieldname).savetostream();
then judge stream's size
if table1.fieldbyname('fieldname').isnull
then //为空
ShowMessage('You forgot the BLOB data!');