SQLite

    case TK_FUNCTION: {
      ExprList *pFarg;       /* List of function arguments */
      if( ExprHasAnyProperty(pExpr, EP_TokenOnly) ){
        pFarg = 0;
      }else{
        pFarg = pExpr->x.pList;
      }
      if( op==TK_AGG_FUNCTION ){
        sqlite3ExplainPrintf(pOut, "AGG_FUNCTION%d:%s(",

                             pExpr->op2, pExpr->u.zToken);
      }else{
        sqlite3ExplainPrintf(pOut, "FUNCTION:%s(", pExpr->u.zToken);
      }
      if( pFarg ){
        sqlite3ExplainExprList(pOut, pFarg);
      }
      sqlite3ExplainPrintf(pOut, ")");
      break;
    }
#ifndef SQLITE_OMIT_SUBQUERY

    if( pA->a[i].sortOrder!=pB->a[i].sortOrder ) return 1;
    if( sqlite3ExprCompare(pExprA, pExprB) ) return 1;
  }
  return 0;
}

/*
** An instance of the following structure is used by the tree walker
** to count references to table columns in the arguments of an 
** aggregate function, in order to implement the
** sqlite3FunctionThisSrc() routine.
*/
struct SrcCount {
  SrcList *pSrc;   /* One particular FROM clause in a nested query */
  int nThis;       /* Number of references to columns in pSrcList */
  int nOther;      /* Number of references to columns in other FROM clauses */
};


/*
** Count the number of references to columns.
*/
static int exprSrcCount(Walker *pWalker, Expr *pExpr){
  if( pExpr->op==TK_COLUMN || pExpr->op==TK_AGG_COLUMN ){
    int i;
    struct SrcCount *p = pWalker->u.pSrcCount;
    SrcList *pSrc = p->pSrc;
    for(i=0; i<pSrc->nSrc; i++){
      if( pExpr->iTable==pSrc->a[i].iCursor ) break;
    }

    if( i<pSrc->nSrc ){
      p->nThis++;
    }else{

      p->nOther++;
    }
  }
  return WRC_Continue;
}

/*
** Determine if any of the arguments to the pExpr Function reference
** pSrcList.  Return true if they do.  Also return true if the function
** has no arguments or has only constant arguments.  Return false if pExpr
** references columns but not columns of tables found in pSrcList.
*/
int sqlite3FunctionUsesThisSrc(Expr *pExpr, SrcList *pSrcList){
  Walker w;
  struct SrcCount cnt;
  assert( pExpr->op==TK_AGG_FUNCTION );
  memset(&w, 0, sizeof(w));
  w.xExprCallback = exprSrcCount;
  w.u.pSrcCount = &cnt;
  cnt.pSrc = pSrcList;
  cnt.nThis = 0;
  cnt.nOther = 0;
  sqlite3WalkExprList(&w, pExpr->x.pList);
  return cnt.nThis>0 || cnt.nOther==0;
}

/*
** Add a new element to the pAggInfo->aCol[] array.  Return the index of
** the new element.  Return a negative number if malloc fails.
*/
static int addAggInfoColumn(sqlite3 *db, AggInfo *pInfo){

          } /* endif pExpr->iTable==pItem->iCursor */
        } /* end loop over pSrcList */
      }
      return WRC_Prune;
    }
    case TK_AGG_FUNCTION: {
      if( (pNC->ncFlags & NC_InAggFunc)==0
       && pWalker->walkerDepth==pExpr->op2
      ){
        /* Check to see if pExpr is a duplicate of another aggregate 
        ** function that is already in the pAggInfo structure
        */
        struct AggInfo_func *pItem = pAggInfo->aFunc;
        for(i=0; i<pAggInfo->nFunc; i++, pItem++){
          if( sqlite3ExprCompare(pItem->pExpr, pExpr)==0 ){

** This file contains routines used for walking the parser tree and
** resolve all identifiers by associating them with a particular
** table and column.
*/
#include "sqliteInt.h"
#include <stdlib.h>
#include <string.h>

/*
** Walk the expression tree pExpr and increase the aggregate function
** depth (the Expr.op2 field) by N on every TK_AGG_FUNCTION node.
** This needs to occur when copying a TK_AGG_FUNCTION node from an
** outer query into an inner subquery.
**
** incrAggFunctionDepth(pExpr,n) is the main routine.  incrAggDepth(..)
** is a helper function - a callback for the tree walker.
*/
static int incrAggDepth(Walker *pWalker, Expr *pExpr){
  if( pExpr->op==TK_AGG_FUNCTION ) pExpr->op2 += pWalker->u.i;
  return WRC_Continue;
}
static void incrAggFunctionDepth(Expr *pExpr, int N){
  if( N>0 ){
    Walker w;
    memset(&w, 0, sizeof(w));
    w.xExprCallback = incrAggDepth;
    w.u.i = N;
    sqlite3WalkExpr(&w, pExpr);
  }
}

/*
** Turn the pExpr expression into an alias for the iCol-th column of the
** result set in pEList.
**
** If the result set column is a simple column reference, then this routine
** makes an exact copy.  But for any other kind of expression, this

** Is equivalent to:
**
**     SELECT random()%5 AS x, count(*) FROM tab GROUP BY random()%5
**
** The result of random()%5 in the GROUP BY clause is probably different
** from the result in the result-set.  We might fix this someday.  Or
** then again, we might not...
**
** The nSubquery parameter specifies how many levels of subquery the
** alias is removed from the original expression.  The usually value is
** zero but it might be more if the alias is contained within a subquery
** of the original expression.  The Expr.op2 field of TK_AGG_FUNCTION
** structures must be increased by the nSubquery amount.
*/
static void resolveAlias(
  Parse *pParse,         /* Parsing context */
  ExprList *pEList,      /* A result set */
  int iCol,              /* A column in the result set.  0..pEList->nExpr-1 */
  Expr *pExpr,           /* Transform this into an alias to the result set */
  const char *zType,     /* "GROUP" or "ORDER" or "" */
  int nSubquery          /* Number of subqueries that the label is moving */
){
  Expr *pOrig;           /* The iCol-th column of the result set */
  Expr *pDup;            /* Copy of pOrig */
  sqlite3 *db;           /* The database connection */

  assert( iCol>=0 && iCol<pEList->nExpr );
  pOrig = pEList->a[iCol].pExpr;
  assert( pOrig!=0 );
  assert( pOrig->flags & EP_Resolved );
  db = pParse->db;
  if( pOrig->op!=TK_COLUMN && zType[0]!='G' ){
    pDup = sqlite3ExprDup(db, pOrig, 0);
    incrAggFunctionDepth(pDup, nSubquery);
    pDup = sqlite3PExpr(pParse, TK_AS, pDup, 0, 0);
    if( pDup==0 ) return;
    if( pEList->a[iCol].iAlias==0 ){
      pEList->a[iCol].iAlias = (u16)(++pParse->nAlias);
    }
    pDup->iTable = pEList->a[iCol].iAlias;
  }else if( ExprHasProperty(pOrig, EP_IntValue) || pOrig->u.zToken==0 ){

  Parse *pParse,       /* The parsing context */
  const char *zDb,     /* Name of the database containing table, or NULL */
  const char *zTab,    /* Name of table containing column, or NULL */
  const char *zCol,    /* Name of the column. */
  NameContext *pNC,    /* The name context used to resolve the name */
  Expr *pExpr          /* Make this EXPR node point to the selected column */
){
  int i, j;                         /* Loop counters */
  int cnt = 0;                      /* Number of matching column names */
  int cntTab = 0;                   /* Number of matching table names */
  int nSubquery = 0;                /* How many levels of subquery */
  sqlite3 *db = pParse->db;         /* The database connection */
  struct SrcList_item *pItem;       /* Use for looping over pSrcList items */
  struct SrcList_item *pMatch = 0;  /* The matching pSrcList item */
  NameContext *pTopNC = pNC;        /* First namecontext in the list */
  Schema *pSchema = 0;              /* Schema of the expression */
  int isTrigger = 0;

          assert( pExpr->x.pList==0 );
          assert( pExpr->x.pSelect==0 );
          pOrig = pEList->a[j].pExpr;
          if( (pNC->ncFlags&NC_AllowAgg)==0 && ExprHasProperty(pOrig, EP_Agg) ){
            sqlite3ErrorMsg(pParse, "misuse of aliased aggregate %s", zAs);
            return WRC_Abort;
          }
          resolveAlias(pParse, pEList, j, pExpr, "", nSubquery);
          cnt = 1;
          pMatch = 0;
          assert( zTab==0 && zDb==0 );
          goto lookupname_end;
        }
      } 
    }

    /* Advance to the next name context.  The loop will exit when either
    ** we have a match (cnt>0) or when we run out of name contexts.
    */
    if( cnt==0 ){
      pNC = pNC->pNext;
      nSubquery++;
    }
  }

  /*
  ** If X and Y are NULL (in other words if only the column name Z is
  ** supplied) and the value of Z is enclosed in double-quotes, then
  ** Z is a string literal if it doesn't match any column names.  In that

        sqlite3ErrorMsg(pParse, "no such function: %.*s", nId, zId);
        pNC->nErr++;
      }else if( wrong_num_args ){
        sqlite3ErrorMsg(pParse,"wrong number of arguments to function %.*s()",
             nId, zId);
        pNC->nErr++;
      }
      if( is_agg ) pNC->ncFlags &= ~NC_AllowAgg;
      sqlite3WalkExprList(pWalker, pList);
      if( is_agg ){
        NameContext *pNC2 = pNC;
        pExpr->op = TK_AGG_FUNCTION;
        pExpr->op2 = 0;
        while( pNC2 && !sqlite3FunctionUsesThisSrc(pExpr, pNC2->pSrcList) ){
          pExpr->op2++;
          pNC2 = pNC2->pNext;
        }
        if( pNC2 ) pNC2->ncFlags |= NC_HasAgg;

        pNC->ncFlags |= NC_AllowAgg;
      }
      /* FIX ME:  Compute pExpr->affinity based on the expected return
      ** type of the function 
      */
      return WRC_Prune;
    }
#ifndef SQLITE_OMIT_SUBQUERY
    case TK_SELECT:

  assert( pEList!=0 );  /* sqlite3SelectNew() guarantees this */
  for(i=0, pItem=pOrderBy->a; i<pOrderBy->nExpr; i++, pItem++){
    if( pItem->iOrderByCol ){
      if( pItem->iOrderByCol>pEList->nExpr ){
        resolveOutOfRangeError(pParse, zType, i+1, pEList->nExpr);
        return 1;
      }
      resolveAlias(pParse, pEList, pItem->iOrderByCol-1, pItem->pExpr, zType,0);
    }
  }
  return 0;
}

/*
** pOrderBy is an ORDER BY or GROUP BY clause in SELECT statement pSelect.

  w.pParse = pParse;
  sqlite3WalkSelect(&w, pSelect);
#endif
}


/*
** This routine sets up a SELECT statement for processing.  The
** following is accomplished:
**
**     *  VDBE Cursor numbers are assigned to all FROM-clause terms.
**     *  Ephemeral Table objects are created for all FROM-clause subqueries.
**     *  ON and USING clauses are shifted into WHERE statements
**     *  Wildcards "*" and "TABLE.*" in result sets are expanded.
**     *  Identifiers in expression are matched to tables.

}

/*
** Reset the aggregate accumulator.
**
** The aggregate accumulator is a set of memory cells that hold
** intermediate results while calculating an aggregate.  This
** routine generates code that stores NULLs in all of those memory
** cells.
*/
static void resetAccumulator(Parse *pParse, AggInfo *pAggInfo){
  Vdbe *v = pParse->pVdbe;
  int i;
  struct AggInfo_func *pFunc;
  if( pAggInfo->nFunc+pAggInfo->nColumn==0 ){
    return;

                         ** TK_REGISTER: register number
                         ** TK_TRIGGER: 1 -> new, 0 -> old */
  ynVar iColumn;         /* TK_COLUMN: column index.  -1 for rowid.
                         ** TK_VARIABLE: variable number (always >= 1). */
  i16 iAgg;              /* Which entry in pAggInfo->aCol[] or ->aFunc[] */
  i16 iRightJoinTable;   /* If EP_FromJoin, the right table of the join */
  u8 flags2;             /* Second set of flags.  EP2_... */
  u8 op2;                /* TK_REGISTER: original value of Expr.op
                         ** TK_COLUMN: the value of p5 for OP_Column
                         ** TK_AGG_FUNCTION: nesting depth */
  AggInfo *pAggInfo;     /* Used by TK_AGG_COLUMN and TK_AGG_FUNCTION */
  Table *pTab;           /* Table for TK_COLUMN expressions. */
#if SQLITE_MAX_EXPR_DEPTH>0
  int nHeight;           /* Height of the tree headed by this node */
#endif
};

/*
** Context pointer passed down through the tree-walk.
*/
struct Walker {
  int (*xExprCallback)(Walker*, Expr*);     /* Callback for expressions */
  int (*xSelectCallback)(Walker*,Select*);  /* Callback for SELECTs */
  Parse *pParse;                            /* Parser context.  */
  int walkerDepth;                          /* Number of subqueries */
  union {                                   /* Extra data for callback */
    NameContext *pNC;                          /* Naming context */
    int i;                                     /* Integer value */
    SrcList *pSrcList;                         /* FROM clause */
    struct SrcCount *pSrcCount;                /* Counting column references */
  } u;
};

/* Forward declarations */
int sqlite3WalkExpr(Walker*, Expr*);
int sqlite3WalkExprList(Walker*, ExprList*);
int sqlite3WalkSelect(Walker*, Select*);

void sqlite3Vacuum(Parse*);
int sqlite3RunVacuum(char**, sqlite3*);
char *sqlite3NameFromToken(sqlite3*, Token*);
int sqlite3ExprCompare(Expr*, Expr*);
int sqlite3ExprListCompare(ExprList*, ExprList*);
void sqlite3ExprAnalyzeAggregates(NameContext*, Expr*);
void sqlite3ExprAnalyzeAggList(NameContext*,ExprList*);
int sqlite3FunctionUsesThisSrc(Expr*, SrcList*);
Vdbe *sqlite3GetVdbe(Parse*);
void sqlite3PrngSaveState(void);
void sqlite3PrngRestoreState(void);
void sqlite3PrngResetState(void);
void sqlite3RollbackAll(sqlite3*,int);
void sqlite3CodeVerifySchema(Parse*, int);
void sqlite3CodeVerifyNamedSchema(Parse*, const char *zDb);

** If the Walker does not have an xSelectCallback() then this routine
** is a no-op returning WRC_Continue.
*/
int sqlite3WalkSelect(Walker *pWalker, Select *p){
  int rc;
  if( p==0 || pWalker->xSelectCallback==0 ) return WRC_Continue;
  rc = WRC_Continue;
  pWalker->walkerDepth++;
  while( p ){
    rc = pWalker->xSelectCallback(pWalker, p);
    if( rc ) break;
    if( sqlite3WalkSelectExpr(pWalker, p)
     || sqlite3WalkSelectFrom(pWalker, p)
    ){
      pWalker->walkerDepth--;
      return WRC_Abort;
    }
    p = p->pPrior;
  }
  pWalker->walkerDepth--;
  return rc & WRC_Abort;
}

# 2012 August 23
#
# The author disclaims copyright to this source code.  In place of
# a legal notice, here is a blessing:
#
#    May you do good and not evil.
#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#***********************************************************************
# This file implements regression tests for SQLite library.
#
# This file implements tests for processing aggregate queries with 
# subqueries in which the subqueries hold the aggregate functions
# or in which the subqueries are themselves aggregate queries
#

set testdir [file dirname $argv0]
source $testdir/tester.tcl

do_test aggnested-1.1 {
  db eval {
    CREATE TABLE t1(a1 INTEGER);
    INSERT INTO t1 VALUES(1), (2), (3);
    CREATE TABLE t2(b1 INTEGER);
    INSERT INTO t2 VALUES(4), (5);
    SELECT (SELECT group_concat(a1,'x') FROM t2) FROM t1;
  }
} {1x2x3}
do_test aggnested-1.2 {
  db eval {
    SELECT
     (SELECT group_concat(a1,'x') || '-' || group_concat(b1,'y') FROM t2)
    FROM t1;
  }
} {1x2x3-4y5}
do_test aggnested-1.3 {
  db eval {
    SELECT (SELECT group_concat(b1,a1) FROM t2) FROM t1;
  }
} {415 425 435}
do_test aggnested-1.4 {
  db eval {
    SELECT (SELECT group_concat(a1,b1) FROM t2) FROM t1;
  }
} {151 252 353}


# This test case is a copy of the one in
# http://www.mail-archive.com/sqlite-users@sqlite.org/msg70787.html
#
do_test aggnested-2.0 {
  sqlite3 db2 :memory:
  db2 eval {
    CREATE TABLE t1 (A1 INTEGER NOT NULL,A2 INTEGER NOT NULL,A3 INTEGER NOT 
    NULL,A4 INTEGER NOT NULL,PRIMARY KEY(A1));
    REPLACE INTO t1 VALUES(1,11,111,1111);
    REPLACE INTO t1 VALUES(2,22,222,2222);
    REPLACE INTO t1 VALUES(3,33,333,3333);
    CREATE TABLE t2 (B1 INTEGER NOT NULL,B2 INTEGER NOT NULL,B3 INTEGER NOT 
    NULL,B4 INTEGER NOT NULL,PRIMARY KEY(B1));
    REPLACE INTO t2 VALUES(1,88,888,8888);
    REPLACE INTO t2 VALUES(2,99,999,9999);
    SELECT (SELECT GROUP_CONCAT(CASE WHEN a1=1 THEN'A' ELSE 'B' END) FROM t2),
            t1.* 
    FROM t1;
  }
} {A,B,B 3 33 333 3333}
db2 close

finish_test