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FROM EHR [ehr_id/value='1234'] CONTAINS COMPOSITION c [openEHR-EHR-COMPOSITION.encounter.v1] CONTAINS |
Node predicate
Node predicate is also a shortcut of standard predicate. It has the following forms:
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matches operator is used in WHERE clause. This operator needs left operand and right operand. Left operand is an AQL identified path. Right operand is enclosed within curly braces. Right operand of matches operator has three forms:
- type of constraint ADL (cADL): this type of right operand can be a value list or a value range. Value range is not supported in the current AQL grammar. Below is an example with matches a string value list:
Code Block SELECT o/data[at0002]/events[at0003]/data/items[at0015]/items[at0018]/name FROM Ehr [uid=$ehrUid] CONTAINS Composition c CONTAINS Observation o[openEHR-EHR-OBSERVATION.microbiology.v1] WHERE o/data[at0002]/events[at0003]/data/items[at0015]/items[at0018]/items[at0019]/items[at0021]/name/defining_code/code_string matches {'18919-1', '18961-3', '19000-9'} - URI: can be either terminology URI or EHR URI, or some other URIS. Only terminology URI is supported in the current AQL grammar. An example with matches a terminology URI is shown below:
Code Block SELECT e/ehr_status/subject/external_ref/id/value, diagnosis/data/items[at0002.1]/value FROM EHR e CONTAINS Composition c[openEHR-EHR-COMPOSITION.problem_list.v1] CONTAINS Evaluation diagnosis[openEHR-EHR-EVALUATION.problem-diagnosis.v1] WHERE c/name/value='Current Problems' AND diagnosis/data/items[at0002.1]/value/defining_code matches { terminology://Snomed-CT/hierarchy?rootConceptId=50043002 } - embedded AQL query: means an AQL query statement, i.e. embedded query, within the curly braces. Embedded query is not supported in the current AQL grammar. It looks like:
Code Block matches {SELECT ... FROM .. WHERE}
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EXISTS is a unary operator, which is always followed by a single operand. The single operand is an AQL identified path. This operator return boolean results: true means the data associated with the specified path exists, false otherwise. EXISTS expression is a single identified expression. The latest grammar only allows this operator in WHERE clause.It may be required as part of openEHR path in future.
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These advanced operators are not yet supported by the grammar. The operator syntax is borrowed from ADL specifications. These are proposed to improve the richness and flexibility of AQL so that AQL syntax supports more complicated query scenarios.
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