set .sql file as variable

I have a powershell script where I set the variable based on a query like this:

    $Query = "SELECT 
                 t1.BSM_NM
                ,t1.D_DTM AS MAXDATETIME
                ,CASE
                    WHEN SUM(t1.V_CUST_BLK_CNT)/SUM(t1.V_ATT_CNT) >= MAX(t2.MAJOR_VOICE_BLOCK) AND SUM(t1.V_CUST_BLK_CNT)/SUM(t1.V_ATT_CNT) < MAX(t2.CRITICAL_VOICE_BLOCK)
                         OR
                         SUM(t1.V_DRP_CALL_CNT)/SUM(t1.V_ATT_CNT) >= MAX(t2.MAJOR_VOICE_DROP) AND SUM(t1.V_DRP_CALL_CNT)/SUM(t1.V_ATT_CNT) < MAX(t2.CRITICAL_VOICE_DROP)
                         OR
                         SUM(t1.V_AXS_F_CNT)/SUM(t1.V_ATT_CNT) >= MAX(t2.MAJOR_VOICE_AXSFAIL) AND SUM(t1.V_AXS_F_CNT)/SUM(t1.V_ATT_CNT) < MAX(t2.CRITICAL_VOICE_AXSFAIL)
                    THEN 1
                    WHEN SUM(t1.V_CUST_BLK_CNT)/SUM(t1.V_ATT_CNT) >= MAX(t2.CRITICAL_VOICE_BLOCK)
                         OR
                         SUM(t1.V_DRP_CALL_CNT)/SUM(t1.V_ATT_CNT) >= MAX(t2.CRITICAL_VOICE_DROP)
                         OR
                         SUM(t1.V_AXS_F_CNT)/SUM(t1.V_ATT_CNT) >= MAX(t2.CRITICAL_VOICE_AXSFAIL)
                    THEN 2
                    ELSE 0
                 END MAJORCRITICAL
                FROM DMSN.DS3R_FH_1XRTT_BTS_LVL_KPI t1
                INNER JOIN
                ZDMSN.DS3R_1XRTT_TRIGGERS_THRESHOLD t2
                ON
                t1.BSM_NM = t2.BSC_NM
                WHERE t1.BSM_NM = 'ARL1' and t1.D_DTM = (SELECT MAX(D_DTM) FROM DS3R_FH_1XRTT_BTS_LVL_KPI WHERE BSM_NM = 'ARL1')
                GROUP BY
                t1.BSM_NM, t1.D_DTM"  

How do I set it to an .sql file instead writing on the query in script itself?