数据库	validationQuery
Oracle	select 1 from dual
MySQL	select 1
Microsoft SQL Server	select 1
DB2	select 1 from sysibm.sysdummy1
SQLite	select 1
HSQLDB	select 1 from INFORMATION_SCHEMA.SYSTEM_USERS
postgresql	select version()
ingres	select 1
Apache Derby	select 1
H2	select 1
Informix	select count(*) from systables