How to do Sql Merge statement on pandas data frame in python

I am new to python dataframes so please help me do a merge on pandas dataframe.

df1

custid   custname    email              phone
 x         tina     z.gmail.com        345-345-3456
 y         mina     z1.gmail.com       445-345-3456
 z         zina     z2.gmail.com       555-345-3456
 q         pina                        233-456-3456

df2

custid   custname    email              phone
 x         tina     z.gmail.com        345-345-3456
 y         xina     z1.gmail.com       445-345-3456
 k         tina     tina@gmail.com    703-234-3456
 q         pina     pina@gmail.com    233-456-3456

I want the desired output.

Insert update and delete .Update should happen if the value in not null in df1.If it is null in df1 and have value in df2 then don't update.

df3

custid   custname    email              phone                    Action
 x         tina     z.gmail.com        345-345-3456               None
 y         mina     z1.gmail.com       445-345-3456               Update
 z         zina     z2.gmail.com       555-345-3456               Insert
 k         tina      tina@gmail.com    703-234-3456               Delete
 q         pina     pina@gmail.com     233-456-3456                 None