Datasheet

RAIS 3.0 Programmer’s Guide – Part I : Advanced Customization

2.3.1.2 Duplicate generator serial number

Example 1 was really simple. Let’s have a look at something more challenging: implement a

consistency check warning about duplicate serial numbers. Serial numbers are optional only

within RAIS 3.0. They hence may not be unique, as this would allow for only one generator

with unknown serial number to be entered in the whole database. So, as uniqueness is not

enforced, it is possible to enter twice the same serial number.

Let’s come quickly back to the query in example 1. Its design is simple, but has one

disadvantage: we may not test it by simply executing it and looking at its result set. This is

due to the fact that we use the field [COMBO Type] directly, which works fine when the

query is executed by the RAIS Interface. It does not work when we want to execute the query

in parallel to a running RAIS Interface, without saving the record. If we are in the unfortunate

situation to face a more complicated consistency check, we definitely want to preview the

result set for debugging purpose. In section 2.6, we introduce custom functions to easily

access control elements in the RAIS Interface, called Interface Access Functions. We will use

those Interface Access Functions in the next consistency check, so be sure that you have

implemented those functions as described in that section 2.6. Then, try this query:

Save it as [Consistency Check – Generator Duplicate Serial Number – Step 1]. Open the

RAIS Interface and enter a new generator. Run and analyze the query, meanwhile changing

the field [Serial Number] (please always assure that you have pressed enter after modifying

the field [Serial Number]). After running the query, you will realize that you do not need to

save the generator record any more for seeing the query results.

The query checks the table of generators and returns all records that match the serial number

we are about to enter for our new generator, i.e. above query returns conflicting records.

Remember the definition of consistency checks: they are successful if they return at least one

record. So what we want to have in fact is the complement of above query. Create this query: