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5.6.2. Where clauses

WhereClause
Figure 5.38. WhereClause

Where clauses are used for filtering (selection operator in the relational algebra).
For each incoming tuple, the expression in the where clause is evaluated to a boolean (possibly converting an atomic to a boolean). if this boolean is true, the tuple is forwarded to the next clause, otherwise it is dropped.
The following query corresponds to "SELECT series FROM captains WHERE name = 'Kathryn Janeway'".
Example 5.109. A where clause.
for $x in collection("captains")
where $x.name eq "Kathryn Janeway"
return $x.series
Result (run with Zorba):
[ "The next generation", "Voyager" ]