title: pointing foreign key to datetime
body: <p>is that possible to make foreign key from datetime datatype ?
  i try this but i got error message : 
  Msg 1776, Level 16, State 0, Line 1
  There are no primary or candidate keys in the referenced table 'penduduk' that match the referencing column list in the foreign key 'tgllahir'.
  Msg 1750, Level 16, State 0, Line 1
  Could not create constraint. See previous errors.</p>
  
  <p>i use this query </p>
  
  <p>PARENT TABLE :</p>
  
  <pre><code>create table penduduk (
  no int identity(1,1),
  noktp char(11) primary key,
  nama varchar(20),
  tgl_lahir datetime NOT NULL,
  namahari varchar(20),
  tgl int,
  bulan int,
  namabulan varchar(20),
  tahun int,
  umur int
  )
  
  CREATE TABLE tua(
  noktp CHAR(11) PRIMARY KEY,
  tgl_lahir datetime NOT NULL CONSTRAINT tgllahir FOREIGN KEY REFERENCES penduduk(tgl_lahir),
  FOREIGN KEY(noktp) REFERENCES penduduk(noktp),
  )
  </code></pre>