Expressions

CASE

The CASE expression evaluates one or more conditions and returns different results depending on which condition is met.

UQL supports two forms of the CASE expression:

• Simple CASE
• Searched CASE

Example Graph

UQL
create().node_schema("Paper").edge_schema("Cites")
create().node_property(@Paper, "title").node_property(@Paper, "score", int32).node_property(@Paper, "author").node_property(@Paper, "publisher").edge_property(@Cites, "weight", int32)
insert().into(@Paper).nodes([{_id:'P1', title:'Efficient Graph Search', score:6, author:'Alex', publisher: "PulsePress"}, {_id:'P2', title:'Optimizing Queries', score:9, author:'Alex'}, {_id:'P3', title:'Path Patterns', score:7, author:'Zack', publisher: "BrightLeaf"}])
insert().into(@Cites).edges([{_from:"P1", _to: "P2", weight: 2}, {_from:"P2", _to: "P3", weight: 1}])

Simple CASE

The simple CASE expression evaluates a single value against multiple possible values, returning the result associated with the first matching value.

Syntax
case <expr>
  when <value_1> then <result_1>
  when <value_2> then <result_2>
  ...
  else <result_default>
end

Details

• <expr> is an expression such as an alias reference, an aggregate function, etc.
• Execution Flow:
  • The <expr> is compared sequentially against each <value_N> specified by the when clause.
  • If <value_N> matches <expr>, the corresponding <result_N> is returned.
  • If no matches are found, the <result_default> specified by the else clause is returned. If else is omitted, null is returned by default.

UQL
find().nodes({@Paper.score > 6}) as n
return case count(n) when 3 then "Y" else "N" end AS result

Result:

Searched CASE

The searched CASE expression evaluates multiple conditions, returning the result associated with the first condition that evaluates to true.

Syntax
case
  when <condition_1> then <result_1>
  when <condition_2> then <result_2>
  ...
  else <result_default>
end

Details

• Each <condition_N> is a boolean value expression that evaluates to true or false.
• Execution Flow:
  • The <condition_N>s are evaluated sequentially.
  • When a <condition_N> evaluates to true, <result_N> is returned immediately.
  • If no <condition_N>s are true, the <result_default> specified by the else clause is returned. If else is omitted, null is returned by default.

UQL
find().nodes({@Paper}) as n
return n.title,
case
  when n.publisher is null then "Publisher N/A"
  when n.score < 7 then -1
  else n.author
end as note

Result: