I've just read CCNA3 Exploration on Chapter 3 about VLAN.

The chapter told that only one VLAN can assign to an interface. but something different in the real world. A switch in my company has been configured one interface can connect to many VLANs. How do they do it?

It's called a trunk interface in Cisco world

Or a voice vlan...

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www.mellowd.co.uk/ccie/

Can you give me an example command?

Port 1 to 4 are VLAN 192.168.10.0
Port 5 to 8 are VLAN 192.168.20.0
Port 9 to 12 are VLAN 192.168.30.0

Port 1 to 4 can connect to file server on Port 24 with IP address 192.168.10.1
Port 5 to 8 can connect to file server on Port 24 with IP address 192.168.20.1
Port 9 to 12 can connect to file server on Port 24 with IP address 192.168.30.1

you can assign subinterfaces and have each subinterfaces on a different VLAN.

You can only configure subinterfaces on routers. You need to use SVIs with switches

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www.mellowd.co.uk/ccie/

So call your first VLAN (192.168.10.0) VLAN 10
Second VLAN (192.168.20.0) VLAN 20
3rd VLAN (192.168.30.0) VLAN 30

Ports 1-4 are in VLAN 10, probably access ports (as in, only one VLAN is supported on this interface, so the device connecting to them does not need to know its own VLAN, the switch will take care of it)
Ports 4-8 are in VLAN 20, probably access ports
Ports 9-12 are in VLAN 30, probably access ports

Port 24 is a trunk port, which is AT LEAST trunking VLANs 10, 20 and 30. By default it will trunk all VLANs unless you've specified which ones you will permit on the trunk.

I hope that helps.....

So just in this example, you're not configuring IPs on interfaces. Just VLANs. So this is a switch. So example config for access ports looks like

interface FastEthernet0/1
switchport mode access
switchport access vlan 10

and the trunk interface

interface FastEthernet0/24
switchport mode trunk
switchport trunk allowed vlan 10,20,30 <--- Note this is optional. If you don't include it, it will trunk all VLANs.