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Updating tuples
The UPDATE command is used to change one or more attribute values
of existing tuples. The WHERE-clause specifies which tuples
should be updated. The SET-clause specifies which attributes should be changed and their new values.
The syntax is:UPDATE <Tablename>SET AttributevaluesWHERE <Condition>;
The assignment of the new value happens as follows:<Attributname> = <Value>
Multiple assingments are separated by commas. The assigned value can either be a constant (absolute term) or the result
of a request, i.e.
there can be a request to the right of the equals sign.
If a whole row is updated, the assignment looks as follows:ROW = ROW(<list of values>)
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