[kvlonge]

Why

Replaying recorded Snowflake results showed three aggregate conversions that disagree with Snowflake:

• COUNT(t.) and COUNT( EXCLUDE ...) counted every row.
• AVG(DISTINCT) of NUMBER(38,0) was typed NUMBER(38,6).
• NULLIF(NULL, x) took the type of x.

Changes

• COUNT of a qualified or EXCLUDE star counts the rows whose selected columns are all non-NULL, as recorded. DISTINCT, a VARIANT column, or a star that selects no column is refused. Only a bare * still counts every row.
• AVG(DISTINCT) of NUMBER(38,0) is NUMBER(38,3), as recorded; other input types refuse until they are recorded.
• NULLIF with a NULL first argument is a NULL typed VARCHAR, as recorded.
• The COUNT and NULLIF rule conditions in the catalogue are updated.

Verification

• The recorded translation cases for COUNT, AVG and NULLIF were replayed on DuckDB. COUNT t004/t005, AVG t005 and NULLIF t003 now match. COUNT(* ILIKE) stays refused, because star ILIKE has no rule yet.
• No repository case regressed.
• New CLI value tests cover COUNT(input.) = 3 beside COUNT() = 5, COUNT(* EXCLUDE b) = 4, AVG(DISTINCT) = 1.500, and COALESCE(NULLIF(NULL, 1), 'none') = 'none'.

[kvlonge]

Closing: SQLQuack lands through local-gate trains, not PR merges (D94), so open PRs only add clutter (D628/D630). The branch is kept. Any work here that isn't on main yet is tracked by the train owner and lands through a train.