Need help with query

Summary:

May I know what is wrong in this query

Content (required):

SELECT

  order_key,

  dfla.source_order_number,

  dfla.source_line_number,

  DFLA.ordered_qty using_requirement_quantity,

  dfla.shipped_qty completed_quantity,

  esib.item_number,

  dfla.request_cancel_date,

  dfla.LAST_UPDATE_DATE

FROM msc_hvgop_consumption mhc,

  msc_system_items msi,

  msc_instance_orgs mio,

  egp_system_items_b esib,

  doo_fulfill_lines_all dfla,

  doo_lines_all dla

WHERE msi.inventory_item_id = substr(mhc.inventory_key,1,instr(mhc.inventory_key,'/',1) -1) --SUBSTR(1,instr(mhc.inventory_key, '/') - 1)

  AND msi.organization_id = SUBSTR(mhc.inventory_key,instr(mhc.inventory_key, '/') + 1)