- Add missing nkSubquery case in lowerExpr so scalar subqueries
(e.g. budget > (SELECT AVG(budget) FROM projects)) are lowered
correctly instead of being treated as NULL literals.
- Move UPDATE SET expression evaluation inside the row loop so
column references (e.g. salary + 5000) are resolved against the
current row, fixing type validation failures.
- Make irAdd/irSub/irMul/irDiv return integer strings when the
result is a whole number, avoiding spurious float output for INT
columns (e.g. MERGE UPDATE qty = 100 + 50 now yields 150).
These fix regressions introduced by switching NULL representation
from empty string to \N, which exposed the pre-existing bugs above.
Refs: issue #9, issue #10
dimgigov
5231724e77