Ora-01779: the column corresponding to the non key value saving table cannot be modified

Problem description

  Error reporting -
SQL error : ORA-01779: The column corresponding to the non key value saving table cannot be modified
01779. 00000 -  "cannot modify a column which maps to a non key-preserved table"
*Cause:    An attempt was made to insert or update columns of a join view which
           map to a non-key-preserved table.
*Action:   Modify the underlying base tables directly.

This error is caused by , Used to update demo_t1 Of demo_t2 surface id Is not the only , Cause the object to be updated test1 A line in may correspond to test2 Many lines in , such oracle I don't know how to update

for example demo_t1 in fname A fmoney '20' Possible corresponding demo_t2 in fname A fmoney '100', ifname A fmoney '200' this 2 Data , Therefore, it is impossible to update . 

terms of settlement

Delete duplicate data to demo_t2 Add a primary key

ALTER TABLE DEMO_T2 ADD PRIMARY KEY(FNAME);

Try it again , The update is successful