USI VS NUSI

Database

USI VS NUSI

Hi Guys,

Can please someone let  me know in which scenario we need to use USI and NUSI.

1 or 2 example would be great.

Thank you,

Naveen

1 REPLY
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Re: USI VS NUSI

Hi Naveen,

SIs in Teradata are rarely used for Joins (different to other DBMSes), so they're usually implemented to get a faster (index-based) access (this is the same in any other DBMS). As you can't force the optimizer to use a SI (no hints), you have to Collect Stats and then check Explain if the SI is used.

USI might also be used for implementing the logical PK (again the same in any DBMS, but hardly done in a DWH).

Dieter