Oracle case when 用法

SELECT B_BRIDGE."ID",B_BRIDGE.BRIDGENAME,V_BRIDGESTATE.STATE,
(case when (V_BRIDGESTATE.SCORE >= 90 and V_BRIDGESTATE.SCORE <= 100) then 'A'
            when (V_BRIDGESTATE.SCORE >= 80 and V_BRIDGESTATE.SCORE <= 89) then 'B'
            when (V_BRIDGESTATE.SCORE >= 66 and V_BRIDGESTATE.SCORE <= 79) then 'C'
            when (V_BRIDGESTATE.SCORE >= 50 and V_BRIDGESTATE.SCORE <= 65) then 'D'
            when (V_BRIDGESTATE.SCORE < 50) then 'E'
       end) as SCORE ,
(case when (V_BRIDGESTATE.STATE = 'red') then '红色报警'
            when (V_BRIDGESTATE.STATE = 'green') then '正常'
            when (V_BRIDGESTATE.STATE = 'yellow') then '黄色报警'
       end) as red 
FROM V_BRIDGESTATE