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 1.425 2009/04/02 17:23:33 danielk1977 Exp $
*/
#include "sqliteInt.h"

/*
** Return the 'affinity' of the expression pExpr if any.
**
** If pExpr is a column, a reference to a column via an 'AS' alias,

  **     SELECT <column> FROM <table>
  **
  ** If this is the case, it may be possible to use an existing table
  ** or index instead of generating an epheremal table.
  */
  p = (ExprHasProperty(pX, EP_xIsSelect) ? pX->x.pSelect : 0);
  if( isCandidateForInOpt(p) ){
    sqlite3 *db = pParse->db;              /* Database connection */

    Expr *pExpr = p->pEList->a[0].pExpr;   /* Expression <column> */
    int iCol = pExpr->iColumn;             /* Index of column <column> */
    Vdbe *v = sqlite3GetVdbe(pParse);      /* Virtual machine being coded */
    Table *pTab = p->pSrc->a[0].pTab;      /* Table <table>. */
    int iDb;                               /* Database idx for pTab */
   
    /* Code an OP_VerifyCookie and OP_TableLock for <table>. */
    iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
    sqlite3CodeVerifySchema(pParse, iDb);
    sqlite3TableLock(pParse, iDb, pTab->tnum, 0, pTab->zName);

    /* This function is only called from two places. In both cases the vdbe
    ** has already been allocated. So assume sqlite3GetVdbe() is always
    ** successful here.
    */
    assert(v);
    if( iCol<0 ){
      int iMem = ++pParse->nMem;
      int iAddr;


      sqlite3VdbeUsesBtree(v, iDb);

      iAddr = sqlite3VdbeAddOp1(v, OP_If, iMem);
      sqlite3VdbeAddOp2(v, OP_Integer, 1, iMem);

      sqlite3OpenTable(pParse, iTab, iDb, pTab, OP_OpenRead);
      eType = IN_INDEX_ROWID;

      sqlite3VdbeJumpHere(v, iAddr);
    }else{
      Index *pIdx;                         /* Iterator variable */

      /* The collation sequence used by the comparison. If an index is to 
      ** be used in place of a temp-table, it must be ordered according
      ** to this collation sequence.  */

      CollSeq *pReq = sqlite3BinaryCompareCollSeq(pParse, pX->pLeft, pExpr);

      /* Check that the affinity that will be used to perform the 
      ** comparison is the same as the affinity of the column. If
      ** it is not, it is not possible to use any index.
      */

      char aff = comparisonAffinity(pX);
      int affinity_ok = (pTab->aCol[iCol].affinity==aff||aff==SQLITE_AFF_NONE);

      for(pIdx=pTab->pIndex; pIdx && eType==0 && affinity_ok; pIdx=pIdx->pNext){
        if( (pIdx->aiColumn[0]==iCol)
         && (pReq==sqlite3FindCollSeq(db, ENC(db), pIdx->azColl[0], -1, 0))
         && (!mustBeUnique || (pIdx->nColumn==1 && pIdx->onError!=OE_None))
        ){

          int iMem = ++pParse->nMem;
          int iAddr;
          char *pKey;
  
          pKey = (char *)sqlite3IndexKeyinfo(pParse, pIdx);
          iDb = sqlite3SchemaToIndex(db, pIdx->pSchema);
          sqlite3VdbeUsesBtree(v, iDb);

# 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.
#
#***********************************************************************
# This file implements regression tests for SQLite library.  The
# focus of this file is testing the SELECT statement.
#
# $Id: select1.test,v 1.66 2009/04/02 17:23:33 danielk1977 Exp $

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

# Try to select on a non-existant table.
#
do_test select1-1.1 {

  }
} {}
do_test select1-14.2 {
  execsql { 
    SELECT 10 IN (SELECT rowid FROM sqlite_master);
  }
} {0}

# Check that ticket #3771 has been fixed.
#
do_test select1-15.1 {
  execsql {
    CREATE TABLE t1(a);
    CREATE INDEX i1 ON t1(a);
    INSERT INTO t1 VALUES(1);
    INSERT INTO t1 VALUES(2);
    INSERT INTO t1 VALUES(3);
  }
} {}
do_test select1-15.2 {
  sqlite3 db2 test.db
  execsql { DROP INDEX i1 } db2
  db2 close
} {}
do_test select1-15.3 {
  execsql { SELECT 2 IN (SELECT a FROM t1) }
} {1}

finish_test