Merging schemas

Question

hi all
we have three schemas in live, now we want to merge all the three schemas into one schema. we have the same set of tables in all the three schema.
we are using sequence to generate unique values .All the tables in all schemas will have their own sequence. coz of this we are having same key values across the schema.
let me explain my example
schema x : table EMP has key value of 100
schema y : table EMP has key value of 100
schema z : table EMP has key value of 100
when i merge the above data to my main schema table i will end up with constraint violation.But i want all the three records in my main schema table
though the key value is same but the record is unique.
also i have child tables depending on the above parent table
if i change the key value also i have to change the dependent column value in the child table.
reply me the feasible approach for the above problem.
--------Keyan -------------------

Answer 1

If you wish to merge the schemas without having to change anything in application,
1. You need to use add a new column to each and every table in each schema (with a different default value for each schema)
2. Populate that with some value for all tables in all schemas
3. Recreate all PKs and FKs in all of the schema to include this new column
4. Export from two other schemas and import into remaining schema
This will ensure that you can merge the schemas but if you wish to differentiate the records inserted thereafter, it would be your business logic.
If you are on 10g, you can make use of DBMS_REDEFINITION to good extent in above steps.