SQLite

**
*************************************************************************
** 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 1.179 2005/09/11 11:56:28 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.

  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 ){


    A->flags |= EP_Distinct;
  }
}
expr(A) ::= ID(X) LP STAR RP(E). {
  A = sqlite3ExprFunction(0, &X);
  sqlite3ExprSpan(A,&X,&E);
}

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains C code routines that are called by the parser
** to handle SELECT statements in SQLite.
**
** $Id: select.c,v 1.268 2005/09/11 11:56:28 drh Exp $
*/
#include "sqliteInt.h"


/*
** Allocate a new Select structure and return a pointer to that
** structure.

    VdbeComment((v, "# skip OFFSET records"));
  }
  if( p->iLimit>=0 && iBreak!=0 ){
    sqlite3VdbeAddOp(v, OP_MemIncr, p->iLimit, iBreak);
    VdbeComment((v, "# exit when LIMIT reached"));
  }
}

/*
** Add code that will check to make sure the top N elements of the
** stack are distinct.  iTab is a sorting index that holds previously
** seen combinations of the N values.  A new entry is made in iTab
** if the current N values are new.
**
** A jump to addrRepeat is made and the K values are popped from the
** stack if the top N elements are not distinct.
*/
static void codeDistinct(
  Vdbe *v,           /* Generate code into this VM */
  int iTab,          /* A sorting index used to test for distinctness */
  int addrRepeat,    /* Jump to here if not distinct */
  int N,             /* The top N elements of the stack must be distinct */
  int K              /* Pop K elements from the stack if indistinct */
){
#if NULL_ALWAYS_DISTINCT
  sqlite3VdbeAddOp(v, OP_IsNull, -N, sqlite3VdbeCurrentAddr(v)+6);
#endif
  sqlite3VdbeAddOp(v, OP_MakeRecord, -N, 0);
  sqlite3VdbeAddOp(v, OP_Distinct, iTab, sqlite3VdbeCurrentAddr(v)+3);
  sqlite3VdbeAddOp(v, OP_Pop, K, 0);
  sqlite3VdbeAddOp(v, OP_Goto, 0, addrRepeat);
  VdbeComment((v, "# skip indistinct records"));
  sqlite3VdbeAddOp(v, OP_IdxInsert, iTab, 0);
}


/*
** This routine generates the code for the inside of the inner loop
** of a SELECT.
**
** If srcTab and nColumn are both zero, then the pEList expressions
** are evaluated in order to get the data for this row.  If nColumn>0

  /* If the DISTINCT keyword was present on the SELECT statement
  ** and this row has been seen before, then do not make this row
  ** part of the result.
  */
  if( hasDistinct ){
    int n = pEList->nExpr;










    codeDistinct(v, distinct, iContinue, n, n+1);
    if( pOrderBy==0 ){
      codeLimiter(v, p, iContinue, iBreak, nColumn);
    }
  }

  switch( eDest ){
    /* In this mode, write each query result to the key of the temporary

** intermediate results while calculating an aggregate.  This
** routine simply stores NULLs in all of those memory cells.
*/
static void resetAccumulator(Parse *pParse, AggInfo *pAggInfo){
  Vdbe *v = pParse->pVdbe;
  int i;
  int addr;
  struct AggInfo_func *pFunc;
  if( pAggInfo->nFunc+pAggInfo->nColumn==0 ){
    return;
  }
  sqlite3VdbeAddOp(v, OP_Null, 0, 0);
  for(i=0; i<pAggInfo->nColumn; i++){
    addr = sqlite3VdbeAddOp(v, OP_MemStore, pAggInfo->aCol[i].iMem, 0);
  }
  for(pFunc=pAggInfo->aFunc, i=0; i<pAggInfo->nFunc; i++, pFunc++){
    addr = sqlite3VdbeAddOp(v, OP_MemStore, pFunc->iMem, 0);
    if( pFunc->iDistinct>=0 ){
      Expr *pE = pFunc->pExpr;
      if( pE->pList==0 || pE->pList->nExpr!=1 ){
        sqlite3ErrorMsg(pParse, "DISTINCT in aggregate must be followed "
           "by an expression");
        pFunc->iDistinct = -1;
      }else{
        KeyInfo *pKeyInfo = keyInfoFromExprList(pParse, pE->pList);
        sqlite3VdbeOp3(v, OP_OpenVirtual, pFunc->iDistinct, 0, 
                          (char*)pKeyInfo, P3_KEYINFO_HANDOFF);
      }
    }
  }
  sqlite3VdbeChangeP2(v, addr, 1);
}

/*
** Invoke the OP_AggFinalize opcode for every aggregate function
** in the AggInfo structure.

  int i;
  struct AggInfo_func *pF;
  struct AggInfo_col *pC;

  pAggInfo->directMode = 1;
  for(i=0, pF=pAggInfo->aFunc; i<pAggInfo->nFunc; i++, pF++){
    int nArg;
    int addrNext = 0;
    ExprList *pList = pF->pExpr->pList;
    if( pList ){
      nArg = pList->nExpr;
      sqlite3ExprCodeExprList(pParse, pList);
    }else{
      nArg = 0;
    }
    if( pF->iDistinct>=0 ){
      addrNext = sqlite3VdbeMakeLabel(v);
      assert( nArg==1 );
      codeDistinct(v, pF->iDistinct, addrNext, 1, 1);
    }
    if( pF->pFunc->needCollSeq ){
      CollSeq *pColl = 0;
      struct ExprList_item *pItem;
      int j;
      for(j=0, pItem=pList->a; !pColl && j<pList->nExpr; j++, pItem++){
        pColl = sqlite3ExprCollSeq(pParse, pItem->pExpr);
      }
      if( !pColl ){
        pColl = pParse->db->pDfltColl;
      }
      sqlite3VdbeOp3(v, OP_CollSeq, 0, 0, (char *)pColl, P3_COLLSEQ);
    }
    sqlite3VdbeOp3(v, OP_AggStep, pF->iMem, nArg, (void*)pF->pFunc, P3_FUNCDEF);
    if( addrNext ){
      sqlite3VdbeResolveLabel(v, addrNext);
    }
  }
  for(i=0, pC=pAggInfo->aCol; i<pAggInfo->nAccumulator; i++, pC++){
    sqlite3ExprCode(pParse, pC->pExpr);
    sqlite3VdbeAddOp(v, OP_MemStore, pC->iMem, 1);
  }
  pAggInfo->directMode = 0;
}

# 2005 September 11
#
# 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.  The
# focus of this script is the DISTINCT modifier on aggregate functions.
#
# $Id: distinctagg.test,v 1.1 2005/09/11 11:56:28 drh Exp $


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

do_test distinctagg-1.1 {
  execsql {
    CREATE TABLE t1(a,b,c);
    INSERT INTO t1 VALUES(1,2,3);
    INSERT INTO t1 VALUES(1,3,4);
    INSERT INTO t1 VALUES(1,3,5);
    SELECT count(distinct a),
           count(distinct b),
           count(distinct c),
           count(all a) FROM t1;
  }
} {1 2 3 3}
do_test distinctagg-1.2 {
  execsql {
    SELECT b, count(distinct c) FROM t1 GROUP BY b ORDER BY b
  }
} {2 1 3 2}

do_test distinctagg-2.1 {
  catchsql {
    SELECT count(distinct) FROM t1;
  }
} {1 {DISTINCT in aggregate must be followed by an expression}}

finish_test

#
# Run this Tcl script to generate the lang-*.html files.
#
set rcsid {$Id: lang.tcl,v 1.100 2005/09/11 11:56:28 drh Exp $}
source common.tcl

if {[llength $argv]>0} {
  set outputdir [lindex $argv 0]
} else {
  set outputdir ""
}

upper-case letters.  The implementation of this function uses the C library
routine <b>toupper()</b> which means it may not work correctly on 
UTF-8 strings.</td>
</tr>
</table>

<p>
The aggregate functions shown below are available by default.  Additional
aggregate functions written in C may be added using the 
<a href="capi3ref.html#sqlite3_create_function">sqlite3_create_function()</a>
API.</p>

<p>
In any aggregate function that takes a single argument, that argument
can be preceeded by the keyword DISTINCT.  In such cases, duplicate
elements are filtered before being passed into the aggregate function.
For example, the function "count(distinct X)" will return the number
of distinct values of column X instead of the total number of non-null
values in column X.
</p>

<table border=0 cellpadding=10>
<tr>
<td valign="top" align="right" width=120>avg(<i>X</i>)</td>
<td valign="top">Return the average value of all non-NULL <i>X</i> within a
group.  Non-numeric values are interpreted as 0.</td>
</tr>

#
# Run this script to generated a omitted.html output file
#
set rcsid {$Id: omitted.tcl,v 1.9 2005/09/11 11:56:28 drh Exp $}
source common.tcl
header {SQL Features That SQLite Does Not Implement}
puts {
<h2>SQL Features That SQLite Does Not Implement</h2>

<p>
Rather than try to list all the features of SQL92 that SQLite does

  DROP COLUMN, ALTER COLUMN, ADD CONSTRAINT, and so forth are omitted.
}

feature {Nested transactions} {
  The current implementation only allows a single active transaction.
}






feature {RIGHT and FULL OUTER JOIN} {
  LEFT OUTER JOIN is implemented, but not RIGHT OUTER JOIN or
  FULL OUTER JOIN.
}

feature {Writing to VIEWs} {
  VIEWs in SQLite are read-only.  You may not execute a DELETE, INSERT, or