HL7 ERQ ERQ
HL7 field reference ERQ fields from HL7 v2.5.1 Show fields
ERQ requests event-related information using an event identifier and optional input parameters.
Query segments define what the sender is asking for, how the receiver should format the answer, and how a multi-message response is continued or limited.
A query is an interface contract. The tag, parameters, row definitions, sort/filter rules, and continuation pointers must match exactly or the receiver may return technically valid data that is not what the requester expected.
The v2.5.1 structures show ERQ in ERP_R09 - ERP R09 and RQQ_Q09 - RQQ Q09. That tells you where it can appear, but the implementation guide still decides which optional fields are meaningful.
For practical interface work, read the generated field panel for datatype, required, repeatable, and table details, then use the notes below to decide what the field should mean in the receiving workflow.
ERQ-1 is the requester's handle for this query. Echoing it back correctly is what lets the requester match a response to the question it asked.
ERQ-2 names the query, event, stored procedure, virtual table, or profile being invoked. This is the semantic switch for the query, so both sides need to agree on the allowed names and their parameter rules.
ERQ-3 carries the criteria or parameters that narrow the query. Keep each parameter in the expected datatype shape and avoid relying on display text that the receiver cannot evaluate.
Repeats should represent separate criteria or parameters in the order the query profile expects, not a free-form pile of search terms.