Query

Modifications by Cursor

When a cursor ranges over the tuples of a base table (i.e., a relation that is stored in the database, rather than a view or a relation constructed by a query), then one can not only read and process the value of each tuple, but one can update or delete tuples. The syntax of

Protecting Against Concurrent Updates

Assume that as we observe the net worths of movie executives using the function worthRanges of Cursors Figure 1, some other process is modifying the underlying MovieExec relation. We shall have more to say about a number of processes accessing a single database at the

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