Re: why data translate error when selecting from view?

[Joe Pluta <joepluta@xxxxxxxxxxxxxxxxx>]

Thatnks for that explanation, Tim.  In a related question: do CTEs allow 
me to effectively "hardcode" the order, causing the SQL engine to work 
in my predefined sequence?

For example, if in this case I did this:

    with t1 as (select * from contr where length(trim(cpcsid)) = 10),
      t2 as (select a.cpcono cono, case ... end csno from t1)
        select * from t2 where csno = 1346100

Would that force the SQL engine to create my T1 in its entirety (thus 
skipping short fields) before then doing the select?  Or is the engine 
just so darned smart that it ignores my sequence and just optimizes me 
into errors?  Of course, upon further reflection, if 
length(trim(cpcsid)) = 10, then no need to check for blanks, so no CASE 
statement.  But I digress...


On 5/16/2019 4:36 PM, Timothy P Clark wrote:
> You can think of the query engine "inlining" the view into the final
> select statement.

<...snip lots of relevant and cool stuff...>


> Keeping in mind that SQL has no rules about predicate evaluation order, it
> should be clear that if the optimizer chooses to evaluate the 2nd
> predicate before the first predicate, we can run into the error you're
> seeing.