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## Changing the visibility of aliases entered in GROUP BY expr AS alias for WHERE {#group-by-expr-alias-where}
Since this version, in a query like
```yql
SELECT foo, ... WHERE foo = 1 GROUP BY expr AS foo
```
the value of foo in `WHERE` is taken from the original table, and not equal to `expr` as it was previously.
To get an error from the query if it changes behavior in this version, you need to add
```yql
PRAGMA FailOnGroupByExprOverride;
```
If you want to keep the previous behavior, you need to transform the query into this form:
```yql
SELECT foo, ... FROM (SELECT expr AS foo ...) WHERE foo = 1 GROUP BY foo
```
If you need to prepare the query for the transition to a new version, it is enough to remove the shadowing of the column name by the alias:
```yql
SELECT foo_new, ... WHERE foo = 1 GROUP BY expr AS foo_new
```
## TODO
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