SQLite

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains routines used for analyzing expressions and
** for generating VDBE code that evaluates expressions in SQLite.
**
** $Id: expr.c,v 1.227 2005/09/09 01:33:19 drh Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>

/*
** Return the 'affinity' of the expression pExpr if any.
**

  int i;
  if( pA==0 ){
    return pB==0;
  }else if( pB==0 ){
    return 0;
  }
  if( pA->op!=pB->op ) return 0;
  if( (pA->flags & EP_Distinct)!=(pB->flags & EP_Distinct) ) return 0;
  if( !sqlite3ExprCompare(pA->pLeft, pB->pLeft) ) return 0;
  if( !sqlite3ExprCompare(pA->pRight, pB->pRight) ) return 0;
  if( pA->pList ){
    if( pB->pList==0 ) return 0;
    if( pA->pList->nExpr!=pB->pList->nExpr ) return 0;
    for(i=0; i<pA->pList->nExpr; i++){
      if( !sqlite3ExprCompare(pA->pList->a[i].pExpr, pB->pList->a[i].pExpr) ){

          if( i>=0 ){
            pItem = &pAggInfo->aFunc[i];
            pItem->pExpr = pExpr;
            pItem->iMem = pParse->nMem++;
            pItem->pFunc = sqlite3FindFunction(pParse->db,
                   pExpr->token.z, pExpr->token.n,
                   pExpr->pList ? pExpr->pList->nExpr : 0, enc, 0);
            if( pExpr->flags & EP_Distinct ){
              pItem->iDistinct = pParse->nTab++;
            }else{
              pItem->iDistinct = -1;
            }
          }
        }
        /* Make pExpr point to the appropriate pAggInfo->aFunc[] entry
        */
        pExpr->iAgg = i;
        pExpr->pAggInfo = pAggInfo;
        return 1;

**
*************************************************************************
** This file contains SQLite's grammar for SQL.  Process this file
** using the lemon parser generator to generate C code that runs
** the parser.  Lemon will also generate a header file containing
** numeric codes for all of the tokens.
**
** @(#) $Id: parse.y,v 1.177 2005/09/09 01:33:19 drh Exp $
*/

// All token codes are small integers with #defines that begin with "TK_"
%token_prefix TK_

// The type of the data attached to each token is Token.  This is also the
// default type for non-terminals.

}
%ifndef SQLITE_OMIT_CAST
expr(A) ::= CAST(X) LP expr(E) AS typetoken(T) RP(Y). {
  A = sqlite3Expr(TK_CAST, E, 0, &T);
  sqlite3ExprSpan(A,&X,&Y);
}
%endif // SQLITE_OMIT_CAST
expr(A) ::= ID(X) LP distinct(D) exprlist(Y) RP(E). {
  A = sqlite3ExprFunction(Y, &X);
  sqlite3ExprSpan(A,&X,&E);
  if( D ){
    sqlite3ErrorMsg(pParse, "DISTINCT in an aggregate function "
        "is not currently supported");
    A->flags |= EP_Distinct;
  }
}
expr(A) ::= ID(X) LP STAR RP(E). {
  A = sqlite3ExprFunction(0, &X);
  sqlite3ExprSpan(A,&X,&E);
}
term(A) ::= CTIME_KW(OP). {
  /* The CURRENT_TIME, CURRENT_DATE, and CURRENT_TIMESTAMP values are

/*
** 2001 September 15
**
** 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.
**
*************************************************************************
** Internal interface definitions for SQLite.
**
** @(#) $Id: sqliteInt.h,v 1.413 2005/09/09 01:33:19 drh Exp $
*/
#ifndef _SQLITEINT_H_
#define _SQLITEINT_H_

/*
** These #defines should enable >2GB file support on Posix if the
** underlying operating system supports it.  If the OS lacks

  int nAccumulator;       /* Number of columns that show through to the output.
                          ** Additional columns are used only as parameters to
                          ** aggregate functions */
  struct AggInfo_func {   /* For each aggregate function */
    Expr *pExpr;             /* Expression encoding the function */
    FuncDef *pFunc;          /* The aggregate function implementation */
    int iMem;                /* Memory location that acts as accumulator */
    int iDistinct;           /* Virtual table used to enforce DISTINCT */
  } *aFunc;
  int nFunc;              /* Number of entries in aFunc[] */
  int nFuncAlloc;         /* Number of slots allocated for aFunc[] */
};

/*
** Each node of an expression in the parse tree is an instance

/*
** The following are the meanings of bits in the Expr.flags field.
*/
#define EP_FromJoin     0x01  /* Originated in ON or USING clause of a join */
#define EP_Agg          0x02  /* Contains one or more aggregate functions */
#define EP_Resolved     0x04  /* IDs have been resolved to COLUMNs */
#define EP_Error        0x08  /* Expression contains one or more errors */
#define EP_Distinct     0x10  /* Aggregate function with DISTINCT keyword */
#define EP_VarSelect    0x20  /* pSelect is correlated, not constant */
#define EP_Dequoted     0x40  /* True if the string has been dequoted */

/*
** These macros can be used to test, set, or clear bits in the 
** Expr.flags field.
*/