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Create constraints in your datawarehouse – why and how

We still see some developers not declaring referential integrity constraints in datawarehouse databases because they think they don’t need it (integrity of data has been validated by the ETL). Here is a small demo I did to show why you need to declare them, and how to do it to avoid any overhead on the ETL.

Test case

I create 3 dimension tables and 1 fact table:

21:01:18 SQL> create table DIM1 (DIM1_ID number, DIM1_ATT1 varchar2(20));
Table DIM1 created.
 
21:01:19 SQL> create table DIM2 (DIM2_ID number, DIM2_ATT1 varchar2(20));
Table DIM2 created.
 
21:01:20 SQL> create table DIM3 (DIM3_ID number, DIM3_ATT1 varchar2(20));
Table DIM3 created.
 
21:01:21 SQL> create table FACT (DIM1_ID number, DIM2_ID number, DIM3_ID number,MEAS1 number);
Table FACT created.

When PDB name conflicts with CDB name

Going to multitenant architecture is not a big change. The administration things (DBA, monitoring, backups) connect to the CDB and the application things connect to the PDB. Without the multitenant option, it is still recommended to go to the CDB architecture. The non-CDB is deprecated and the multitenant architecture brings interesting features. People often ask how to name the CDB and the PDB, especially when they have naming rules or policies in the company. My recommendation is to name the PDB as you are used to naming the databases: the name often gives an idea of the data that is inside, the application, and the environment. The CDB is the container, and in my opinion, you should apply the same naming rules as for servers. Don’t forget that pluggable databases are made to be moved across CDB, so the CDB name should not depend on the content.