{#
  safe_numeric(col)
  Casts a string column to numeric, treating any non-numeric value as NULL.
  Handles all EES suppression codes (z, c, x, q, u, etc.) without needing
  an explicit list — any string that doesn't look like a number becomes NULL.
  A trailing percent sign is accepted: DfE's 2023/24 KS2 information file
  writes percentages as "34%" (audit C2).
#}
{% macro safe_numeric(col) -%}
    CASE WHEN {{ col }} ~ '^-?[0-9]+(\.[0-9]+)?%?$' THEN rtrim({{ col }}, '%')::numeric ELSE NULL END
{%- endmacro %}