Seven things I really hate in database design

1. Common prexif in all table names
   eg: TXXX, TYYY, TZZZ, VAAA, VBBB - T stays for Table, V stays for View
   eg: APPXXX, APPYYY, APPZZZ - APP is an application name
2. Common prefix in all field names in every table
   eg: APPXXX.XXX_FIELD_A, APPXXX.XXX_FIELD_B, APPXXX.XXX_FIELD_C
3. Fields with the same meaning and different names (in different tables)
   es: TABLE_A.BANK_ID, TABLE_B.BK_CODE
4. Fields with the same logical type and different physical types
   eg: TABLE_A.MONEY_AMOUNT NUMBER(20,2)
TABLE_B.MONEY_AMOUNT NUMBER(20,0) – value * 100
   TABLE_B.MONEY_AMOUNT VARCHAR(20) –value * 100 as char
5. No foreign-keys nor integrity constraints at all - by design
6. Date (or generally structured data type) representation with generic and not specific types
   eg: TABLE_A.START_DATE NUMBER(8,0) – yyyyddmm as int
   eg: TABLE_B.START_DATE VARCHAR(8) – yyyyddmm as char
7. (possible only in presenceof 6.) Special values for semantic corner-cases which are syntactically invalid
   eg: EXPIRY_DATE = 99999999 – represents “never expires case”,
   but… IT’S NOT A VALID DATE!!! - why not 99991231??