SQLite

      sqlite3IdListDelete(db, pSrc->a[i+iFrom].pUsing);
      assert( pSrc->a[i+iFrom].fg.isTabFunc==0 );
      pSrc->a[i+iFrom] = pSubSrc->a[i];
      iNewParent = pSubSrc->a[i].iCursor;
      memset(&pSubSrc->a[i], 0, sizeof(pSubSrc->a[i]));
    }
    pSrc->a[iFrom].fg.jointype = jointype;

    /* For every result column in the outer query that does not have an AS
    ** clause, if that column is a reference to an output column from the
    ** inner query, then preserve the name of the column as it was written
    ** in the original SQL text of the outer query by added an AS clause.
    ** This prevents the outer query column from taking on a name derived
    ** from inner query column name.
    **
    ** Example:
    **     CREATE TABLE t1(a,b);
    **     CREATE VIEW v1(x,y) AS SELECT a,b FROM t1;
    **     SELECT x,y FROM v1;
    **
    ** The inner "v1" subquery will get flattened into the outer query.  After
    ** flattening, the outer query becomes:  "SELECT a,b FROM t1".  But the
    ** new query gives column names of "a" and "b", not the "x" and "y" that
    ** the programmer expected.  This step adds AS clauses so that the
    ** flattened query becomes:  "SELECT a AS x, b AS y FROM t1".
    **
    ** This is not a perfect solution.  The added AS clause is the same text as
    ** the original input SQL.  So if the input SQL used goofy column names
    ** like "SELECT v1.X,(y) FROM v1", then the added AS clauses will be those
    ** same goofy colum names "v1.X" and "(y)", not just "x" and "y".  We could
    ** improve that, but doing so might break lots of legacy code that depends
    ** on the current behavior which dates back to around 2004.
    **
    ** Update on 2017-07-29:  The AS clause is only inserted into outer query
    ** result columns that get substituted for inner query columns.  Formerly
    ** an AS clause was added to *all* columns in the outer query that did not
    ** already have one, even columns that had nothing to do with the inner
    ** query.
    */
    pList = pParent->pEList;
    for(i=0; i<pList->nExpr; i++){
      Expr *p;
      if( pList->a[i].zName==0
       && (p = pList->a[i].pExpr)->op==TK_COLUMN
       && p->iTable==iParent
      ){
        char *zName = sqlite3DbStrDup(db, pList->a[i].zSpan);
        sqlite3Dequote(zName);
        pList->a[i].zName = zName;
      }
    }

    /* Now begin substituting subquery result set expressions for 
    ** references to the iParent in the outer query.
    ** 
    ** Example:
    **
    **   SELECT a+5, b*10 FROM (SELECT x*3 AS a, y+10 AS b FROM t1) WHERE a>b;
    **   \                     \_____________ subquery __________/          /
    **    \_____________________ outer query ______________________________/
    **
    ** We look at every expression in the outer query and every place we see
    ** "a" we substitute "x*3" and every place we see "b" we substitute "y+10".
    */








    if( pSub->pOrderBy ){
      /* At this point, any non-zero iOrderByCol values indicate that the
      ** ORDER BY column expression is identical to the iOrderByCol'th
      ** expression returned by SELECT statement pSub. Since these values
      ** do not necessarily correspond to columns in SELECT statement pParent,
      ** zero them before transfering the ORDER BY clause.
      **