Select query with join condition error

Question

I have a select query to get a result set and my query is as follows:

 SELECT T0."REFID", T0."REFID_NR", T0."ID_POS", 
 CASE 
    WHEN T4."REFID" IS NOT NULL 
    THEN T4."REFID"
 END AS "result"
FROM "SYSTEM"."T00_SOFT" T0
LEFT OUTER JOIN 
(
SELECT T1."REFID", T1."REFID_NR", T1."ID_POS",T1."ARTIKEL" ,T2."VEHW", T2."VNHW" , 
(((T2."VEHW"*100)/(T2."VNHW"))*((T1."ER_AW"*100)))/(T1."BAS_AW") AS "claims"
FROM "SYSTEM"."T00_SOFT" T1
INNER JOIN "SYSTEM"."T00_EG" T2
ON T1."REFID" = T2."REFID"
AND T1."ORGID_WE" = T2."ORGID"
AND T1."ARTIKEL" = T2."MATNR" ) T4;

When I execute the query I get the following error:

Could not execute 'SELECT T0."REFID", T0."REFID_NR", T0."ID_POS", CASE WHEN T4."REFID" IS NOT NULL THEN ...' in 42 ms 382 µs . 
SAP DBTech JDBC: [257] (at 521): sql syntax error: line 15 col 33 (at pos 521)

Here line 15 refers to the last line and indicates that the error exists at T4. I dont find anything missing. If anyone can suggest what would be gthe problem?

Thanks

Answer 1

You are missing the ON criteria in your join between T0 and T4. I would rework your query as:

SELECT T0."REFID", T0."REFID_NR", T0."ID_POS", 
 CASE 
    WHEN T4."REFID" IS NOT NULL 
    THEN T4."REFID"
 END AS "result"
FROM "SYSTEM"."T00_SOFT" T0
LEFT OUTER JOIN 
    (
    SELECT T1."REFID", T1."REFID_NR", T1."ID_POS",T1."ARTIKEL" ,T2."VEHW", T2."VNHW" , 
    (((T2."VEHW"*100)/(T2."VNHW"))*((T1."ER_AW"*100)))/(T1."BAS_AW") AS "claims"
    FROM "SYSTEM"."T00_SOFT" T1
        INNER JOIN "SYSTEM"."T00_EG" T2
            ON T1."REFID" = T2."REFID"
                AND T1."ORGID_WE" = T2."ORGID"
                AND T1."ARTIKEL" = T2."MATNR" ) T4
    ON T0."REFID" = T4."REFID"

You had joined T0 and T4 without describing how they were related. Remember, just because you defined how TOO_SOFT and TOO_EG are related in your subquery in the From clause does not imply how T0 and T4 are related. According to a reference manual I found here, join criteria are always required with Left and Right Outer Joins.

Also, I would hesitate to use a Case statement without an Else statement because if the case is not true then it will return NULL. If that's what you want, great, but I suspect you would benefit from programming in an alternative rather than leaving the Else statement out altogether.

Answer 2

 SELECT T0."REFID", T0."REFID_NR", T0."ID_POS", 
 CASE 
    WHEN T4."REFID" IS NOT NULL 
    THEN T4."REFID"       ---<-- T4 is a Table Alias you need to mention 
 END AS "result"               -- the column name as well like T4.ColumnName

if you are only checking against possible nulls in your column your can use ISNULL function and provide a substitute value if returned value is null.

something like this....

 SELECT T0."REFID"
       , T0."REFID_NR"
       , T0."ID_POS"
       , IFNULL(T4."REFID",'Sub_Value') AS "Result"