sqlserver:
SELECT CONVERT(VARCHAR, 日期字段, 112) AS XXX
SELECT FORMAT(日期字段, 'yyyyMMDDHHmmss') AS XXX
mysql
SELECT DATE_FORMAT(日期字段, '%Y%m%d%H%i%s') AS XXX
postgres
SELECT TO_CHAR(日期字段, 'YYYYMMDDHH24MI') AS XXX
SQLite
SELECT strftime('%Y%m%d%H%M%S', 日期字段) AS XXX
Oracle
SELECT TO_CHAR(日期字段, 'YYYYMMDDHH24MISS') AS XXX