• mhansson/martin@linux-st28.site's avatar
    Bug#32848: Data type conversion bug in union subselects in MySQL 5.0.38 · 867a7865
    mhansson/martin@linux-st28.site authored
    There were two problems when inferring the correct field types resulting from
    UNION queries.
    - If the type is NULL for all corresponding fields in the UNION, the resulting 
      type would be NULL, while the type is BINARY(0) if there is just a single 
      SELECT NULL.
    - If one SELECT in the UNION uses a subselect, a temporary table is created
      to represent the subselect, and the result type defaults to a STRING type,
      hiding the fact that the type was unknown(just a NULL value).
    Fixed by remembering whenever a field was created from a NULL value and pass
    type NULL to the type coercion if that is the case, and creating a string field
    as result of UNION only if the type would otherwise be NULL.
    867a7865
union.result 41.1 KB