SELECT DISTINCT --fields
FROM table1 a, table2 b, table3 c, table4 d 
WHERE a.line_cd = b.line_cd 
AND a.line_cd = 21
--other conditions
AND a.clm_seq_no = 7100003
AND d.eff_dt = (SELECT MAX(eff_dt)
		  FROM table4
		   WHERE 1=1
		     AND srvc_code = a.srvc_code 
		     AND line_cd = a.line_cd 
		     AND sched_no = a.sched_no 
		     AND cover_code = a.cover_code 
		     AND eff_dt <= :global.variable --problem
                )