Oracle case when 用法

select a.MARC_REC_NO,(case marc_use_flag  when '1' then '订购'  when '2' then '待编'  when '3' then '已编'  when '4' then '审校'  end) as marc_use_flag,MARC_TYPE,CATA_OPER,CATA_DATE,LANG_CODE,DOC_TYPE_CODE,M_CALL_NO,M_TITLE,M_AUTHOR,M_PUBLISHER,M_PUB_YEAR,M_ISBN ,b.ASORD_NO,GET_MODE_CODE,CARRIER_CODE,PUBL_FREQ,KIND_NO,(case PERI_TYPE   when '0' then '正常刊'   when '1' then '改名刊'   when '2' then '停刊'   when '3' then '停定刊' end) as PERI_TYPE,PERI_ORD_QTY,PERI_PRICE,PERI_TOTAL_PRICE,REMARK,(case ORD_FLAG   when '0' then '未发订'   when '1' then '已发订' end) as ORD_FLAG from  marc  a ,PERI_ORD_DETL b where a.marc_rec_no =b.marc_rec_no and b.peri_ord_cata_id='4BE9F5BA819749C984CE13D922E22C87'