Snowflake Create Projection Policy

Before writing a CREATE PROJECTION POLICY statement:

1. Read references/parameters.md to review all available parameters and their defaults.
2. For each parameter, decide whether the user's request implies a non-default value.
3. Include only the parameters that differ from the default or that the user explicitly requested — do not bloat the DDL with unnecessary clauses.
4. Never use CREATE OR REPLACE — always use CREATE PROJECTION POLICY IF NOT EXISTS.
5. The policy body must call PROJECTION_CONSTRAINT(ALLOW => {TRUE|FALSE} [, ENFORCEMENT => {'FAIL'|'NULLIFY'}]).
6. ALLOW => TRUE permits column projection (pass-through); ALLOW => FALSE restricts it — use the ENFORCEMENT argument to control whether restricted queries fail or return NULLs.
7. The default ENFORCEMENT is FAIL; only specify NULLIFY if the user explicitly wants columns silently nullified rather than causing query failures.
8. Projection policies only affect columns in the final result set (outermost SELECT); columns used only in WHERE or JOIN clauses are not blocked. Requires Enterprise Edition or higher.