How to merge two iphoto libraries

Question

How do I merge two Iphoto libraries

Answer 1

Actually it can be done on the command line.  This will be quite tedious if the library you are transferring is large.
Log into the computer on which you want the merged library to reside. 
Then, go to Applications->Utilities, and launch the Terminal.
At the prompt, cd to the following directory:
Lydias-MacBook-Pro:~ lydiachet$ cd Pictures/iPhoto\ Library/Auto\ Import
Now launch an ftp session with the computer where your other library resides:
Lydias-MacBook-Pro:Auto Import lydiachet$ ftp 192.168.1.36
Connected to 192.168.1.36.
220 192.168.1.36 FTP server (tnftpd 20080929) ready.
Name (192.168.1.36:lydiachet): carolchet
331 User carolchet accepted, provide password.
Password:
230 User carolchet logged in.
Remote system type is UNIX.
Using binary mode to transfer files.
On the remote computer, cd to the Masters directory in the iPhoto library:
ftp> cd Pictures/iPhoto\ Library/Masters
The directory tree from here down is listed by year, month and date, so actual directories will vary: in the example I'm looking in a directory from July 21, 2012:
ftp> cd 2012/07/21
250 CWD command successful.
ftp> ls
229 Entering Extended Passive Mode (|||62595|)
150 Opening ASCII mode data connection for '/bin/ls'.
total 0
drwxr-xr-x  12 carolchet  staff  408 Jul 21 11:29 20120721-112923
226 Transfer complete.
Now cd to the only directory found here:
ftp> cd 20120721-112923
View the photo files using the ls command:
ftp> ls
229 Entering Extended Passive Mode (|||62596|)
150 Opening ASCII mode data connection for '/bin/ls'.
total 5
-rw-------  1 carolchet  staff  231082 Jul 21 11:04 IMG_0035.JPG
-rw-------  1 carolchet  staff  249389 Jul 21 11:04 IMG_0036.JPG
-rw-------  1 carolchet  staff  253379 Jul 21 11:04 IMG_0037.JPG
-rw-------  1 carolchet  staff  270819 Jul 21 11:05 IMG_0038.JPG
-rw-------  1 carolchet  staff  253501 Jul 21 11:05 IMG_0039.JPG
-rw-------  1 carolchet  staff  243288 Jul 21 11:05 IMG_0040.JPG
-rw-------  1 carolchet  staff  248939 Jul 21 11:05 IMG_0041.JPG
-rw-------  1 carolchet  staff  287363 Jul 21 11:06 IMG_0042.JPG
-rw-------  1 carolchet  staff  248358 Jul 21 11:07 IMG_0044.JPG
-rw-------  1 carolchet  staff  268819 Jul 21 11:08 IMG_0045.JPG
226 Transfer complete.
ftp>
from this point you can copy the files to the local computer using mget
ftp> mget *.JPG
If you have lots of pictures this will be tedious as you then need to navigate through the diretory trees until you have copied all the photos. 
Good news is, next time you launch iPhoto on the local computer, it will automatically import all of the new files.