Trying to convert oracle sql to Sql Server date for a migration activity

Below is the oracle SQL query currently used in the existing system, I am trying to convert this SQL into a SQL Server query for the new system.

I have been trying different format, but I am not successful and also since I am experienced in Oracle than SQL Server.

Kindly help me in this regard.

 SELECT DISTINCT
        b.CONTRACT_KEY,
        b.STARTDATE,
        b.ENDDATE,
        CASE
            WHEN MULTI_YEAR_FLAG = 'N' THEN null
            WHEN TRUNC(b.ENDDATE, 'Y') <= TRUNC(SYSDATE, 'Y') THEN null
            WHEN TRUNC(TO_DATE(EXTRACT (YEAR FROM SYSDATE) || '-' || EXTRACT (MONTH FROM b.STARTDATE) || 
                 '-' || EXTRACT (DAY FROM b.STARTDATE_UPDATED), 'YYYY-MM-DD'),'Q') >= TRUNC(SYSDATE, 'Q')
                THEN TO_DATE(EXTRACT (YEAR FROM SYSDATE) || '-' || EXTRACT (MONTH FROM b.STARTDATE) || 
                     '-' || EXTRACT (DAY FROM b.STARTDATE_UPDATED), 'YYYY-MM-DD')
            WHEN TRUNC(TO_DATE(EXTRACT (YEAR FROM ADD_MONTHS(SYSDATE,12)) || '-' || EXTRACT (MONTH FROM 
                 b.STARTDATE) || '-' || EXTRACT (DAY FROM b.STARTDATE_UPDATED), 'YYYY-MM-DD'),'Y') 
                 < TRUNC(b.ENDDATE, 'Y')
                THEN TO_DATE(EXTRACT (YEAR FROM ADD_MONTHS(SYSDATE,12)) || '-' || EXTRACT (MONTH FROM 
                   b.STARTDATE) 
                     || '-' || EXTRACT (DAY FROM b.STARTDATE_UPDATED), 'YYYY-MM-DD')
        END "NEXT_MYA_DATE"
 FROM 
     SALES_ENT.CONTRACT_N_DIM_BT b

Answer

Based Martin’s suggestion, i worked through and made the sql to work finally. Thanks again.

SELECT DISTINCT
    b.contract_key,
    b.startdate,
    b.enddate,
    CASE
        --Non Multi-Year
        WHEN multi_year_flag = 'N'                                                      THEN
            NULL
        --Contracts expiring in current year or before
        WHEN CAST(datepart(year, b.enddate) AS INT) <= CAST(datepart(year, getdate()) AS INT) THEN
            NULL
        --Contracts with anniversary in current year
        WHEN datepart(quarter, b.startdate) >= datepart(quarter, getdate())
        --cast(datepart(YEAR, getdate() as int) + '-' + cast(datepart(MONTH, b.STARTDATE) as INT) + '-' + cast(datepart(DAY, b.STARTDATE_UPDATED) as INT), 'YYYY-MM-DD'),'Q') >= TRUNC(SYSDATE, 'Q')
         THEN
            datepart(year, getdate()) + '-' + datepart(month, b.startdate) + '-' + datepart(day, b.startdate_updated)
        --Contracts with anniversary next year
        WHEN datepart(year, dateadd(month, 12, getdate())) < datepart(year, b.enddate)  THEN
            datepart(year, dateadd(month, 12, getdate())) + '-' + datepart(month, b.startdate) + '-' + datepart(day, b.startdate_updated
            )
    END "NEXT_MYA_DATE",
    FROM
    sales_ent.contract_n_dim_bt   b