Newbie - Querying data based on dates and comparing it to a different fixed date for each row

Transact-SQL
1

I need to be able to get the SUM_RESULT (based on the SUM_DATE) right before the EVENT_DATE (just the one closest to it as it can be any date) and then the first SUM_RESULT at least 12 months from the EVENT_DATE. This is my query so far but I have multiple rows at present for each patient.

SELECT PATIENT_INFO.PATIENT_SURNAME, PATIENT_INFO.PATIENT_GIVEN_NAME, PATIENT_INFO.PATIENT_DOB, PATIENT_INFO.PATIENT_MRN, CLIN_VISITS_SUM.SUM_DATE, CLIN_VISITS_SUM.SUM_RESULT,
CLIN_ANZDATA_EVENT.EVENT_DATE, CLIN_ANZDATA_EVENT.EVENT_DESC, LU_ANZEVENTS_1.ANZEVT_ID, LU_PATVISIT_COL.PATCOL_DESC, CLIN_VISIT_TYPE.visit_date
FROM PATIENT_INFO LEFT OUTER JOIN
CLIN_VISITS_SUM ON PATIENT_INFO.PATIENT_ID = CLIN_VISITS_SUM.PATIENT_ID LEFT OUTER JOIN
CLIN_VISIT_TYPE ON CLIN_VISITS_SUM.PATCOL_ID = CLIN_VISIT_TYPE.PATCOL_ID LEFT OUTER JOIN
LU_PATVISIT_COL ON CLIN_VISITS_SUM.PATCOL_ID = LU_PATVISIT_COL.PATCOL_ID LEFT OUTER JOIN
CLIN_ANZDATA_EVENT ON PATIENT_INFO.PATIENT_ID = CLIN_ANZDATA_EVENT.PATIENT_ID LEFT OUTER JOIN
LU_ANZEVENTS ON CLIN_ANZDATA_EVENT.ANZEVT_SERIES = LU_ANZEVENTS.ANZEVT_SERIES LEFT OUTER JOIN
LU_ANZEVENTS AS LU_ANZEVENTS_1 ON CLIN_ANZDATA_EVENT.ANZEVT_SERIES = LU_ANZEVENTS_1.ANZEVT_SERIES
WHERE (LU_ANZEVENTS_1.ANZEVT_ID = 'G') AND (LU_PATVISIT_COL.PATCOL_DESC = 'eGFR') AND (CLIN_VISITS_SUM.SUM_DATE >= CLIN_ANZDATA_EVENT.EVENT_DATE)

Any help would be greatly appreciated. Thank you

2

If you supply DDL, Sample Data and expected results, then we can provide better help, otherwise we're just guessing and go back and forth