“Hey, every once in a while the secondary form works better than the original, but it's certainly a rarity.”
Teradata Primary and Secondary Index Cheat Sheet
A table has only one Primary Index, but it can have up to 32 Secondary Indexes.
There are two types of secondary indexes and they are Unique (USI) and Non-Unique (NUSI).
Use an USI in the SQL WHERE clause and it results in a 2 second two AMP retrieve.
Use a NUSI in the SQL WHERE clause and it is an all AMP retrieve, but not a full table scan.
|Unique Primary Index (UPI)||Non-Unique Primary Index (NUPI)|
|SELECT * FROM Employee_Table WHERE Employee_No = 12345;||SELECT * FROM Order_Table WHERE Customer_No ...|