<code> select a1, a2, a1+a2 as ta from (select 0 as a1, 0 as a2); </code> The expression aliases are considered part of the query output, usable in grouping, sorting, and any more-outer queries.
<code> select a1, a2, a1+a2 as ta from (select 0 as a1, 0 as a2); </code> The expression aliases are considered part of the query output, usable in grouping, sorting, and any more-outer queries.