Tag: databases

They eliminate Full Table Scans.

Duplicate row checks are avoided.

There is no overhead involved.

They are best used for range queries.

You cannot insert rows with a duplicate USI value.

True

False

All columns required by the query are available via the Primary index.

All columns required by the query are available via a Join Index.

All columns required by the query are available via the Hash Index

The PE covers the query by looking into cache to see if the same query has been run in the last 240 minutes. If it has been cached the PE doesn't have to generate steps for the AMPs.

Join Indexes have repeating values.

Join Indexes do not have repeating values.

Join Indexes are updated automatically when their underlying rows change

Join Indexes are not updated automatically when their underlying rows change.

Downtime

Stability

Performance

Volatility

True

False

BETWEEN

IN

HAVING

ALIAS

each SELECT statement within the UNION has the same number of columns

The columns have similar data types

the columns in each SELECT statement are in same order.

None

MAX( )

MID( )

SUM( )

NOW( )

True

False