INVOKE in the Out-list of a SELECT Statement

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You can use INVOKE as an expression in the out-list of a SELECT statement. This makes it possible to use a single statement to retrieve values from a database table and from a component. The syntax is:

SELECT col1, (INVOKE MyComp.MyMethod1),  

(INVOKE    MyComp.MyMethod2


SELECT col2, col3)

FROM Employee

This syntax is the same syntax that is used by many database vendors for supporting subqueries in the out-list.

The INVOKE in the out-list can be used in combination with ORDER BY/GROUP BY and HAVING.

INVOKE cannot return more than one record. So when a query protocol is being invoked, only 0 or 1 records can be returned. If the INVOKE returns more records an error will occur and the statement will fail.

By default, an INVOKE returns a string with maximum size of 32K. You can use the TO_CLOB() SQL function to tell the INVOKE to return the long string correctly without it being truncated.