Getting syntax error with Union sub query in Sybase DB

Question

We have a table ta_service with following data

Ref_id         seq         desc

2340                        1             Service 1
2340                        2             Offer 1
2340                        3             Service 2
2340                        4             Offer 2
2340                        5             Service 3
2340                        5             Service 4

We have a requirement of fetching the services which has offers and we dont have any reference for getting this data apart from Ref_id(foreign key) and seq(Primary key) column.

We tried to fetch by following query but failed with that.

SELECT * FROM ta_service
WHERE Ref_id = 2340 AND seq IN ( 
    SELECT seq-1 AS seq
    FROM ta_service
    WHERE Ref_id = 2340
    AND desc LIKE '%Offer%'
UNION 
    SELECT seq AS seq
    FROM ta_service
    WHERE Ref_id = 2340
    AND desc LIKE '%Offer%'
        ORDER BY seq) 

we are using sybase database. Any help appreciated

Answer 1

ASE doesn't support UNION in any subqueries.

You can refer the Sybase Documentation

Answer 2

Here is the link to sybase manual which says UNION is not supported in subqueries: http://infocenter.sybase.com/help/index.jsp?topic=/com.sybase.infocenter.dc36272.1570/html/commands/X56548.htm

However I noticed that if we have the union clause within a derived table expression, then, it works fine. Here is the link to sybase manual which gives the syntax for the query: http://infocenter.sybase.com/archive/index.jsp?topic=/com.sybase.help.ase_15.0.sqlug/html/sqlug/sqlug418.htm

Example of failing and working query given below:

Mocked use case: Get employees from either department D1 or D2.

Failing query:

SELECT empname from emp WHERE deptid IN 
(SELECT deptid from dept WHERE deptid = "D1"
UNION
SELECT deptid from dept WHERE deptid = "D2")

Working query:  With additional select and derived table based on union:

SELECT empname from emp WHERE deptid IN (
SELECT deptid FROM 
(SELECT deptid from dept WHERE deptid = "D1"
UNION
SELECT deptid from dept WHERE deptid = "D2") derivedTable
)

Answer 3

Assuming you are using ASE, your ORDER BY needs to go outside the subquery.

From the Sybase Documentation:

•Subqueries cannot manipulate their results internally, that is, a subquery cannot include the order by clause, the compute clause, or the into keyword.

Answer 4

You should remove order by, and enclose desc in " because it's keyword

SELECT * FROM ta_service
WHERE Ref_id = 2340 
AND seq IN ( 
    SELECT seq-1 AS seq
    FROM ta_service
    WHERE Ref_id = 2340
    AND "desc" LIKE '%Offer%'
UNION 
    SELECT seq AS seq
    FROM ta_service
    WHERE Ref_id = 2340
    AND "desc" LIKE '%Offer%'
    ) 

Answer 5

ASE doesn't support UNION in a subquery as the 12.5 SQL manual I've just referred to confirms. It says "You cannot include a for browse clause or a union in a subquery." on page 169 in chapter 5. Another answer is correct even if the link was to IQ. I'd have left a comment but my account doesn't allow it.