ご了承ください:
データ型には DATE を使用しました。ある患者が正午前にある病院を訪れ、午後に別の病院を訪れる可能性があります。その場合、DATETIME を使用します。
パーティショニングでのソートでは、record_id の前に dt_admit を使用して、任意の順序でデータを入力できるようにします。
CREATE TABLE #hdata(
record_id INT NOT NULL IDENTITY(1,1) PRIMARY KEY,
patient_id INT NOT NULL,
hospital_id INT NOT NULL,
dt_admit DATE NOT NULL,
dt_discharge DATE NULL
);
INSERT INTO #hdata(
patient_id,
hospital_id,
dt_admit,
dt_discharge
)
VALUES (
1,
1,
'2012-02-01',
'2012-02-03'
), (
2,
1,
'2012-02-01',
'2012-02-04'
), (
1,
2,
'2012-03-04',
'2012-03-04'
);
-- 1/ link each record to the previous record for each patient, NULL if none
SELECT
record_id,
patient_id,
ROW_NUMBER() OVER (PARTITION BY patient_id ORDER BY dt_admit,record_id) AS visit_seq_id
INTO
#visit_sequence
FROM
#hdata;
SELECT
v1.record_id,
v1.patient_id,
v2.record_id AS previous_record_id
FROM
#visit_sequence AS v1
LEFT JOIN #visit_sequence AS v2 ON
v2.patient_id=v1.patient_id AND
v2.visit_seq_id=v1.visit_seq_id-1
ORDER BY
v1.record_id;
DROP TABLE #visit_sequence;
-- 2/ criteria on linked records: same hospital, previous visit < 7 days
SELECT
record_id,
patient_id,
hospital_id,
dt_admit,
ROW_NUMBER() OVER (PARTITION BY patient_id,hospital_id ORDER BY dt_admit,record_id) AS visit_seq_id
INTO
#visit_sequence_elab
FROM
#hdata;
SELECT
v1.record_id,
v1.patient_id,
v2.record_id AS previous_record_id
FROM
#visit_sequence_elab AS v1
LEFT JOIN #visit_sequence_elab AS v2 ON
v2.patient_id=v1.patient_id AND
v2.hospital_id=v1.hospital_id AND
v2.visit_seq_id=v1.visit_seq_id-1 AND
DATEDIFF(DAY,v1.dt_admit,v2.dt_admit)<7
ORDER BY
v1.record_id;
DROP TABLE #visit_sequence_elab;
DROP TABLE #hdata;