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5.6.2. Where clauses

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 $ eq "Kathryn Janeway"
return $x.series
Result (run with Zorba):
[ "The next generation", "Voyager" ]