Need some help with a SPT syntax to get all the data.

This is my current SQL string:

*testString = "Select * From webprddt6.resmngt2" +;
" Join webprddt6.resmngt3 On webprddt6.resmngt2.recseq = webprddt6.resmngt3.projindex" +;
" Join webprddt6.resmngt3b On webprddt6.resmngt3.recseq = webprddt6.resmngt3b.taskindex" +;
" Where assigned = ''"

This work as long as resmngt3b table has records that match the resmngt3 table but it fails to give me the records in resmngt3 that have not been asigned at all.