尝试decode在select语句中使用a的别名时，我遇到了标题中所述的错误。这是代码：

SELECT DISTINCT rl.complaint_date, 
                  decode(rl.judgement_date,null,rl.complaint_amt,rl.judgement_amt) as account_amt, 
                  rl.date_served1, 
                  rl.date_served2,
                  rl.judgement_date,         
                  rl.skip_locate,
                  rl.case_no,
                  lcc.bal_range_min, 
                  lcc.bal_range_max, 
                  lcc.cost_range_min, 
                  lcc.cost_range_max, 
                  lcc.court,
                  lcc.county AS lcc_county,
                  ah.ACCOUNT, 
                  ah.transaction_code, 
                  ah.transaction_date, 
                  ah.rule_id, 
                  ah.amount, 
                  ah.description,                    
                  r.state, 
                  r.zip_code, 
                  z.county AS ah_county,
                  z.county_2,
                  z.county_3,
                  z.county_4
  FROM legal_address_skip las,
       racctrel r, 
       ziplist z, 
       legal_court_cost lcc, 
       racctlgl rl,
       legal_transaction_review ah
  WHERE ah.ACCOUNT = rl.ACCOUNT
  AND ah.ACCOUNT = las.ACCOUNT(+)
  AND ah.ACCOUNT = r.ACCOUNT
  AND nvl(lpad(substr(r.zip_code,0,instr(r.zip_code,'-')-1),5,0), substr(r.zip_code,1,5)) = z.zip 
  AND r.state = lcc.state
  AND (REPLACE(lcc.county,' ','') = REPLACE(upper(z.county),' ','') 
       OR REPLACE(lcc.county,' ','') = REPLACE(upper(z.county_2),' ','')
       OR REPLACE(lcc.county,' ','') = REPLACE(upper(z.county_3),' ','')
       OR REPLACE(lcc.county,' ','') = REPLACE(upper(z.county_4),' ',''))
  AND lcc.transaction_code = ah.transaction_code
  AND lcc.transaction_code = 1
  AND lcc.end_date IS NULL
  AND ah.amount NOT BETWEEN lcc.cost_range_min AND lcc.cost_range_max
  AND (account_amt NOT BETWEEN lcc.bal_range_min AND lcc.bal_range_max
      OR lcc.bal_range_min - account_amt NOT BETWEEN 0 AND 500)
  ORDER BY CASE 
           WHEN ah.amount NOT BETWEEN lcc.cost_range_min AND lcc.cost_range_max THEN 1
           WHEN ah.amount BETWEEN lcc.cost_range_min AND lcc.cost_range_max THEN 2 END, ah.amount;

我之前在select语句中使用过别名，因此我对为什么会收到此错误感到困惑。在这种情况下，它的工作方式是否有所不同？