Sql server 将数据从DateTime2（4）数据类型字段迁移到一个数据类型字段，以时间戳（4）表示，时区截断为毫秒

例如：

DateTime2(4):   SQL Server       
-----------------------------
2017-03-30 15:10:15.1234

-----------------------------
Timestamp(4) With Time Zone: PostgreSQL
-----------------------------
2017-03-30 15:10:15.123
-----------------------------

我使用firedac Configure TFDDataMove的组件迁移数据，如下所示：

FDTable1.Active:= False;
FDDataMove1.CommitCount:=100;
FDDataMove1.StatictsInterval:=100;
FDDataMove1.TextDataDef.StrEmpty2Null:=False;
FDDataMove1.Mode:=dmAlwaysInsert;
FDDataMove1.Options:= [poOptimiseDest,poOptimiseSrc,poClearDest,poAbortOnExc,poIdentityInsert];
FDDataMove1.Source:=FDQuery2;
FDDataMove1.Destination:=FDTable2;


Version SQL SERVER: 2014
Version PostgreSQL: 9.6.3 
Version Firedac: 11.0.1(Build 73709)
Version Rad Studio: RAD Studio XE7


    =================================================
    Client info:
    =================================================
    Loading Driver PG...
    Client brand = PostgreSQL regular
    Client version = 906040000
    Client DLL name: C\...\Proyect_Migration\bin\libpg.dll

    =================================================
    Session info
    =================================================
    Current catalog =
    Current schema = public
    Server version = 9.6.3
    Server Encoding = UTF8
    Client Encoding = UTF8
    Is Superuser = on
    Session Authorization = postgres
    date Style = ISO,DMY
    Integer date/time = on
    Time zone = America/Mexico_City
    Standard conforming string = on 

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问题是什么？为什么要截断毫秒