can you do an ELSE WHEN on a CASE

Question

CASE WHEN P.NURSING_UNIT is not null THEN P.NURSING_UNIT ELSE '' END NURSING_UNIT
    ,CASE WHEN P.UNIT_CODE is not null THEN P.UNIT_CODE ELSE '' END UNIT_CODE, 
    CASE WHEN M.SIGN_DATE IS NOT NULL THEN 'COMPLETED' ELSE 
    WHEN M.SIGN_DATE IS NULL THEN 'UNCOMPLETED' AS ASSESSMENTS

error: because the sp is not compiling now. getting this error message: Msg 156, Level 15, State 1, Procedure GET_SCHEDULE_ALL_DETAIL, Line 18 Incorrect syntax near the keyword 'WHEN'. Msg 156, Level 15, State 1, Procedure GET_SCHEDULE_ALL_DETAIL, Line 25 Incorrect syntax near the keyword 'AND'.

    ----

    USE [PRO]
    GO

    /****** Object: StoredProcedure [dbo].[GET_SCHEDULE_ALL_DETAIL] Script Date: 11/02/2011 14:14:50 ******/
    SET ANSI_NULLS ON
    GO

    SET QUOTED_IDENTIFIER ON
    GO


    alter PROC [dbo].[GET_SCHEDULE_ALL_DETAIL]
    @FACILITYKEY varchar(1000),
    @UNITSTR VARCHAR(100),
    @FromDate datetime,
    @ToDate datetime
    AS
    BEGIN

    (SELECT S.FACILITY_KEY, S.PAT_NUMBER, S.A3A_DATE_USER, M.REFERENCE_DATE ,
    RTRIM(P.LAST_NAME) + CASE WHEN RTRIM(P.FIRST_NAME) <> '' THEN ', '
    ELSE ''
    END + RTRIM(P.FIRST_NAME) PATIENT_NAME
    ,CASE WHEN P.NURSING_UNIT is not null THEN P.NURSING_UNIT ELSE '' END NURSING_UNIT
    ,CASE WHEN P.UNIT_CODE is not null THEN P.UNIT_CODE ELSE '' END UNIT_CODE, 
    CASE WHEN M.SIGN_DATE IS NOT NULL THEN 'COMPLETED' ELSE 
    WHEN M.SIGN_DATE IS NULL THEN 'UNCOMPLETED' AS ASSESSMENTS
    FROM [PC].MDS_M_SCHEDULE S INNER JOIN OPTC.MD3_M_MAST M
    ON S.PAT_NUMBER=M.PAT_NUMBER
    LEFT JOIN OGEN.GEN_M_PATIENT_MAST P ON S.PAT_NUMBER = P.PAT_NUMBER
    WHERE S.PAT_NUMBER=M.PAT_NUMBER AND M.REFERENCE_DATE < GETDATE()
    AND S.A3A_DATE_USER BETWEEN @FromDate AND @ToDate
    AND S.FACILITY_KEY IN (SELECT Value FROM dbo.ListToTable(@FACILITYKEY,','))
    AND ( @UNITSTR IS NULL
    OR @UNITSTR = ''
    OR CHARINDEX(P.UNIT_CODE, @UNITSTR)% 2 = 1 ))

    UNION ALL

    (SELECT * FROM (
    (SELECT S.FACILITY_KEY, S.PAT_NUMBER, S.A3A_DATE_USER, M.REFERENCE_DATE ,
    RTRIM(P.LAST_NAME) + CASE WHEN RTRIM(P.FIRST_NAME) <> '' THEN ', '
    ELSE ''
    END + RTRIM(P.FIRST_NAME) PATIENT_NAME
    ,CASE WHEN P.NURSING_UNIT is not null THEN P.NURSING_UNIT ELSE '' END NURSING_UNIT
    ,CASE WHEN P.UNIT_CODE is not null THEN P.UNIT_CODE ELSE '' END UNIT_CODE, 'LATE' AS ASSESSMENTS
    FROM [PC].MDS_M_SCHEDULE S INNER JOIN OPTC.MD3_M_MAST M
    ON S.PAT_NUMBER=M.PAT_NUMBER
    LEFT JOIN OGEN.GEN_M_PATIENT_MAST P ON S.PAT_NUMBER = P.PAT_NUMBER
    WHERE M.REFERENCE_DATE < GETDATE() AND S.A3A_DATE_USER BETWEEN @FromDate AND @ToDate
    AND ( @UNITSTR IS NULL
    OR @UNITSTR = ''
    OR CHARINDEX(P.UNIT_CODE, @UNITSTR)% 2 = 1 )
    ) --Started

    UNION ALL

    (SELECT S.FACILITY_KEY, S.PAT_NUMBER, S.A3A_DATE_USER, NULL AS REFERENCE_DATE,
    RTRIM(P.LAST_NAME) + CASE WHEN RTRIM(P.FIRST_NAME) <> '' THEN ', '
    ELSE ''
    END + RTRIM(P.FIRST_NAME) PATIENT_NAME
    ,CASE WHEN P.NURSING_UNIT is not null THEN P.NURSING_UNIT ELSE '' END NURSING_UNIT
    ,CASE WHEN P.UNIT_CODE is not null THEN P.UNIT_CODE ELSE '' END UNIT_CODE, 'LATE' AS ASSESSMENTS
    FROM [PC].MDS_M_SCHEDULE S INNER JOIN OPTC.MD3_M_MAST M
    ON S.PAT_NUMBER=M.PAT_NUMBER
    LEFT JOIN OGEN.GEN_M_PATIENT_MAST P ON S.PAT_NUMBER = P.PAT_NUMBER
    WHERE S.PAT_NUMBER NOT IN (SELECT M.PAT_NUMBER FROM [PC].MD3_M_MAST M)
    AND S.A3A_DATE_USER < GETDATE() AND S.A3A_DATE_USER BETWEEN @FromDate AND @ToDate
    AND ( @UNITSTR IS NULL
    OR @UNITSTR = ''
    OR CHARINDEX(P.UNIT_CODE, @UNITSTR)% 2 = 1 )) --Not Started
    ) LATE
    WHERE FACILITY_KEY IN (SELECT Value FROM dbo.ListToTable(@FACILITYKEY,',')))

    END

    GO

Answer 1

No, ELSE is a catch-all. In your example, it's not clear why you would want to include a condition in the ELSE clause, since you've already checked the logically opposite condition in the first WHEN expression.

However, more generally, you can nest CASE expressions, which would look something like this:

CASE
  WHEN m.sign_date IS NOT NULL THEN 'COMPLETED'
  ELSE
    CASE WHEN m.start_date IS NOT NULL THEN 'IN PROGRESS' ELSE 'NOT STARTED' END
END