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Type versus Representation Confusion in SQL
This describes how a value might have two or more distinct representations. For example, user-defined type POINT might have a declared possrep based on Cartesian coordinates and another based on polar coordinates. SQL has a system-defined type, TIMESTAMP, for values representing points in time, a timestamp being represented by a date, a time of day, and-optionally-a time zone, expressed as a displacement from UTC. Clearly any timestamp can be expressed in several different ways, using different time zones.
Three o'clock in the afternoon of December 31st, 2011 in UK, for example, is the same time as two o'clock in the morning of January 1st, 2012 in New Zealand. SQL treats those two representations as distinct values that compare equal, in like fashion to its treatment of character strings with trailing blanks, with similar consequences. If instead it had treated them as distinct representations of the same value, then the issue of indeterminacy would not have arisen.
Special cases of projection This section describes the identity projection, r {ALL BUT}, and the projection on no attributes, r { }, which yields TABLE_DUM when r is empty, ot
Using Invoker Rights: By default, the stored procedure executes with the privileges of its definer, not its invoker. These procedures are bound to the schema in which they inh
Using FORALL and BULK COLLECT Together You can unite the BULK COLLECT clause with the FORALL statement, in that case, the SQL engine bulk-binds column values incrementally. In
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Providing Results of Queries Expressing queries in SQL is the (big) subject. Here I present just a simple example to give you the flavour of things to come in those chapters.
Cause of Indeterminacy in SQL One root cause of indeterminacy in SQL lies in its implementation of comparison for equality. For certain system-defined types it is possible for
%ROWCOUNT When its cursor or cursor variable is opened, the %ROWCOUNT is zeroed. Before the first fetch, the %ROWCOUNT yields 0. Afterward, it yields the number of rows fetche
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