Does SQLScript for SAP HANA support the use of INSERT with CTEs (Common Table Expressions)?

问题

I know this isn't a specific bit of code or problem, but I am having trouble with a very similar issue to the person asking this (except theirs is for SQL Server): Combining INSERT INTO and WITH/CTE ...and I can't seem to find it out there on any SAP HANA help forums etc. so thought there may be an expert on here who can just give me a simple yes or no answer.

The SQL statement I am using contains multiple CTEs, but when I try to insert it tells me there is a Syntax error around the word INSERT. It is definitely laid out exactly the same as in the question I've linked above (spent hours checking), and I can post code samples if necessary but I simply want to know whether it is supported first! Thanks

回答1:

Short answer: No, CTEs are not supported for INSERT/UPDATE statements.

Longer answer: SQLScript's INSERT/UPDATE commands are actually "borrowed" SQL commands as the documentation explains.

Checking the documentation for SQL INSERT we find that it supports a subquery as a source of values.

The subquery term is defined as part of the SQL SELECT statement. Checking the documentation for SELECT shows that <subquery> and <with_clause> are different, non-overlapping terms.

This means, that CTEs cannot be used in subqueries and therefore not be part of the subqueries used in INSERT/UPDATE commands.

You can, however, use SQLScript table variables in INSERT statements in your SQLScript blocks, which is very similar to CTEs:

DO BEGIN
  te_a := SELECT 10, 'xyz' as VAL from dummy;
  te_b := SELECT 20, 'abc' as VAL from dummy;

  te_all :=     SELECT * from :te_a
      UNION ALL SELECT * from :te_b;

  INSERT INTO VALS 
             (SELECT * from :te_all);

END;

回答2:

You can convert the CTE into a Sub-Select statement in many cases

You can use following

insert into city (city, countryid, citycode)
select
    city, countryid, citycode
from (
    -- CTE Expression as subselect
    select * from city
    -- end (CTE)
) cte

Instead of using following valid CTE command combined with INSERT (on SQL Server)

with cte as (
    select * from city
)
insert into city (city, countryid, citycode)
select
    city, countryid, citycode
from cte

回答3:

SAP HANA includes this posibility, the order of the code is different than SQL Server:

INSERT INTO EXAMPLE (ID)
 WITH cte1 AS (SELECT 1 AS ID FROM DUMMY)
 SELECT ID FROM cte1;

来源：https://stackoverflow.com/questions/48748810/does-sqlscript-for-sap-hana-support-the-use-of-insert-with-ctes-common-table-ex

标签

sap

sql-insert

common-table-expression

hana

hana-sql-script