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# trailing_value_expr

> The value a trailing window aggregates: `value_col`, masked to NULL where the row is not a valid observation.

The value a trailing window aggregates: `value_col`, masked to NULL where the row is not a valid observation. CASE, not FILTER -- DuckDB does not support FILTER in ordered-set aggregates inside window functions, which is why int\_lap\_thermal\_proxy used to pre-aggregate with a GROUP BY and reach forward as a result.

## Signature

```sql theme={null}
{{ trailing_value_expr(value_col, valid_condition=none) }}
```


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