Neoview SQL Reference Manual (R2.4)

MVGROUPs
An MVGROUP is a group of materialized views that are refreshed together. One way to group
MVs is by the frequency of the REFRESH (for example, each day, each week, each month).
Another way is to create groups to preserve consistency, that is, to group all the MVs on common
tables.
An MV can be added to an MVGROUP only when it satisfies at least one of these conditions:
• all the MVs that are used by it, directly or indirectly, are also in the group
• the MV is single-delta
• the MV is a RECOMPUTE MV
This ensures that every MV in the group is consistent with a well-defined state of the database
tables after a REFRESH. A single-delta MV is defined as an ON REQUEST MV that can be
refreshed based on changes (delta) to a single table. A single-delta MV must satisfy the
requirement that the MV is based either on a single table (base table or MV) or on a join where
only one of the base tables is not included in the IGNORE CHANGES clause.
MVGROUPS are automatically created for every table used by MVs. Those MVGROUPS have
the same name as their corresponding base table. As MVs are created, they are automatically
added to the MVGROUP of their corresponding base tables. To refresh all the MVs on a specific
base table, use the “MAINTAIN Command” (page 210).
Although MVGROUPs are automatically created, if you decide to group together materialized
views that share the same refresh frequency rate, you will need to manually create them.
264 SQL Language Elements