可以通过以下sql语句查询syscolumns表中字段对应的类型。
如果列不允许NULL值，coltype值将增加256。要确定此类列的数据类型，请从值中减去256，并根据可能的coltype值计算余数。例如，如果coltype值为262，则减去256会留下6的余数，表示该列具有SERIAL数据类型。
select a.tabname,b.colname,b.coltype,
case b.coltype
when '0' then 'CHAR'
when '1' then 'SMALLINT'
when '2' then 'INTEGER'
when '3' then 'FLOAT'
when '4' then 'SMALLFLOAT'
when '5' then 'DECIMAL'
when '6' then 'SERIAL'
when '7' then 'DATE'
when '8' then 'MONEY'
when '9' then 'NULL'
when '10' then 'DATETIME'
when '11' then 'BYTE'
when '12' then 'TEXT'
when '13' then 'VARCHAR'
when '14' then 'INTERVAL'
when '15' then 'NCHAR'
when '16' then 'NVARCHAR'
when '17' then 'INT8'
when '18' then 'SERIAL8'
when '19' then 'SET'
when '20' then 'MULTISET'
when '21' then 'LIST'
when '22' then 'Unnamed ROW'
when '23' then 'COLLECTION'
when '40' then 'LVARCHAR'
when '41' then 'CLOB'
when '43' then 'BLOB'
when '44' then 'BOOLEAN'
when '256' then 'CHAR'
when '257' then 'SMALLINT'
when '258' then 'INTEGER'
when '259' then 'FLOAT'
when '260' then 'REAL'
when '261' then 'DECIMAL'
when '262' then 'SERIAL'
when '263' then 'DATE'
when '264' then 'MONEY'
when '266' then 'DATETIME'
when '267' then 'BYTE'
when '268' then 'TEXT'
when '269' then 'VARCHAR'
when '270' then 'INTERVAL'
when '271' then 'NCHAR'
when '272' then 'NVARCHAR'
when '273' then 'INT8'
when '274' then 'SERIAL8'
when '275' then 'SET'
when '276' then 'MULTISET'
when '277' then 'LIST'
when '278' then 'Unnamed ROW'
when '296' then 'LVARCHAR'
when '297' then 'CLOB'
when '298' then 'BLOB'
when '299' then 'BOOLEAN'
when '4118' then 'Named ROW'
end as coltypename,
b.colno
from systables a left join syscolumns b
on a.tabid=b.tabid where a.tabid>99 and a.tabtype='T'
order by a.tabname,b.colno;