SQLite

**           a GROUP BY clause.  But such a HAVING clause is also harmless
**           so there does not appear to be any reason to add extra logic
**           to suppress it. **)
**
**   (2) The inner query is the recursive part of a common table expression.
**
**   (3) The inner query has a LIMIT clause (since the changes to the WHERE
**       clause would change the meaning of the LIMIT).
**
**   (4) The inner query is the right operand of a LEFT JOIN and the
**       expression to be pushed down does not come from the ON clause
**       on that LEFT JOIN.
**
**   (5) The WHERE clause expression originates in the ON or USING clause
**       of a LEFT JOIN where iCursor is not the right-hand table of that
**       left join.  An example:
**
**           SELECT *
**           FROM (SELECT 1 AS a1 UNION ALL SELECT 2) AS aa
**           JOIN (SELECT 1 AS b2 UNION ALL SELECT 2) AS bb ON (a1=b2)
**           LEFT JOIN (SELECT 8 AS c3 UNION ALL SELECT 9) AS cc ON (b2=2);
**
**       The correct answer is three rows:  (1,1,NULL),(2,2,8),(2,2,9).
**       But if the (b2=2) term were to be pushed down into the bb subquery,
**       then the (1,1,NULL) row would be suppressed.
**
**   (6) The inner query features one or more window-functions (since 
**       changes to the WHERE clause of the inner query could change the 
**       window over which window functions are calculated).
**
** Return 0 if no changes are made and non-zero if one or more WHERE clause
** terms are duplicated into the subquery.
*/
static int pushDownWhereTerms(
  Parse *pParse,        /* Parse context (for malloc() and error reporting) */
  Select *pSubq,        /* The subquery whose WHERE clause is to be augmented */
  Expr *pWhere,         /* The WHERE clause of the outer query */
  int iCursor,          /* Cursor number of the subquery */
  int isLeftJoin        /* True if pSubq is the right term of a LEFT JOIN */
){
  Expr *pNew;
  int nChng = 0;
  if( pWhere==0 ) return 0;
  if( pSubq->selFlags & SF_Recursive ) return 0;  /* restriction (2) */

#ifndef SQLITE_OMIT_WINDOWFUNC
  if( pSubq->pWin ) return 0;
#endif

#ifdef SQLITE_DEBUG
  /* Only the first term of a compound can have a WITH clause.  But make
  ** sure no other terms are marked SF_Recursive in case something changes
  ** in the future.
  */
  {

do_execsql_test 9.3 {
  WITH aaa(x, y, z) AS (
    SELECT x, y, max(y) OVER xyz FROM t4
    WINDOW xyz AS (ORDER BY x)
  )
  SELECT *, min(z) OVER (ORDER BY x) FROM aaa ORDER BY 1;
} {1 g g g   2 i i g   3 l l g   4 g l g   5 a l g   6 m m g}

#-------------------------------------------------------------------------
#
do_execsql_test 10.0 {
  CREATE TABLE sales(emp TEXT PRIMARY KEY, region, total);
  INSERT INTO sales VALUES
      ('Alice',     'North', 34),
      ('Frank',     'South', 22),
      ('Charles',   'North', 45),
      ('Darrell',   'South', 8),
      ('Grant',     'South', 23),
      ('Brad' ,     'North', 22),
      ('Elizabeth', 'South', 99),
      ('Horace',    'East',   1);
}

# Best two salespeople from each region
#
do_execsql_test 10.1 {
  SELECT emp, region, total FROM (
    SELECT 
      emp, region, total,
      row_number() OVER (PARTITION BY region ORDER BY total DESC) AS rank
    FROM sales
  ) WHERE rank<=2 ORDER BY region, total DESC
} {
  Horace      East     1
  Charles     North   45
  Alice       North   34
  Elizabeth   South   99
  Grant       South   23
}

finish_test