Oracle 查詢中判斷語句的寫法case when then else end

在查詢時可能會根據某個條件來判斷顯示數據，此時就用到case語句 下面是一個查詢示例： SELECT distinct a.certiType, a.certiNo, a.policyNo, d.riskCode, a.agentCode, (case when 'P' = a.certitype then b.sumpremium else c.chgpremium end ) as sumpremium, (select sacmain.disrate from sacmain where policyNo = a.policyno) as rate, d.confirmNo, d.uploadFlag FROM sarealpayfee a, sacmain b, sapmain c, sapolicyuploadplatformlog d, sacitemcar e WHERE a.policyno = b.policyno(+) and a.policyno = e.policyno(+) and a.certino = c.endorseno(+) and a.certino = d.certino and a.agentCode is not null and nvl(d.uploadFlag, 0) in ('0', '1') and a.accountno = '2120151103445' and a.riskCode in ('0332', '0335') and nvl(e.usenaturecode, 0) not in ('309009', '309008', '301006001', '301006002') and nvl(a.chagFlag, 0) <> '2' and (d.settleno is null or d.settleno = '2120151103445')