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TIMEWINDOW P2Y/2006-01-01 |
Grammar
How to write an AQL query statement manually
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- EHR class expression. You need to determine whether this query is applied to a single EHR or all EHRs. The latter is called population queries. If it is for all EHRs, you don't need to specify ehr_id/value in FROM clause. Otherwise, you need to either specify a specific value or use a query parameter for ehr_id/value in FROM clause. For this particular scenario, it is for a single EHR. Parameter called ehrUid is used for the ehr_id/value, I would have this AQL query statement:
No Format FROM EHR [ehr_id/value=$ehrUid]
- Archetype expressions.
- To write archetype expressions in the FROM clause, we need to determine what archetypes are required in the scenario. Since archetypes are used to represent clinical concepts. The easy way to identify archetypes from a scenario is to identify clinical concepts mentioned in the scenario. Each clinical concept is generally associated with one archetype. Two clinical concepts are mentioned in the aforementioned scenario: blood pressure and health encounter. These concepts are used to identify two archetypes used in query: an observation archetype with archetype id - openEHR-EHR-OBSERVATION.blood_pressure.v1, and a composition archetype with archetype id - openEHR-EHR-COMPOSITION.encounter.v1.
- Determine whether we need a variable name for each archetype class expression or not. We may need one if the reference to the archetype class expression is required by other AQL clauses. At the moment, I don't put any variable names for the archetype expressions. The two archetype expressions are:
No Format COMPOSITION [openEHR-EHR-COMPOSITION.encounter.v1] OBSERVATION [openEHR-EHR-OBSERVATION.blood_pressure.v1]
- Containment expression. openEHR RM is used to identify the hierarchical relationships among the found archetypes so as to define the containment expression. For example, a composition archetype is the parent of an observation archetype, so the AQL query would look like:
No Format FROM EHR [ehr_id/value=$ehrUid] CONTAINS COMPOSITION [openEHR-EHR-COMPOSITION.encounter.v1] CONTAINS OBSERVATION [openEHR-EHR-OBSERVATION.blood_pressure.v1]
Step 2. Write WHERE clause
WHERE clause represents all query criteria that cannot be represented in the FROM clause. To write WHERE clause expression, you need to:
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