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 1.199 2005/05/23 15:06:39 drh Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>

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

  }

  pExpr->iTable = -1;
  while( pNC && cnt==0 ){
    SrcList *pSrcList = pNC->pSrcList;
    ExprList *pEList = pNC->pEList;


    /* assert( zTab==0 || pEList==0 ); */
    if( pSrcList ){
      for(i=0, pItem=pSrcList->a; i<pSrcList->nSrc; i++, pItem++){
        Table *pTab = pItem->pTab;
        Column *pCol;
  
        if( pTab==0 ) continue;

      for(j=0; j<pEList->nExpr; j++){
        char *zAs = pEList->a[j].zName;
        if( zAs!=0 && sqlite3StrICmp(zAs, zCol)==0 ){
          assert( pExpr->pLeft==0 && pExpr->pRight==0 );
          pExpr->op = TK_AS;
          pExpr->iColumn = j;
          pExpr->pLeft = sqlite3ExprDup(pEList->a[j].pExpr);
          cnt = 1;
          assert( zTab==0 && zDb==0 );
          goto lookupname_end_2;
        }
      } 
    }

    /* 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;
    }
  }

  /*
  ** 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
  ** case, we need to return right away and not make any changes to
  ** pExpr.
  **
  ** Because no reference was made to outer contexts, the pNC->nRef
  ** fields are not changed in any context.
  */
  if( cnt==0 && zTab==0 && pColumnToken->z[0]=='"' ){
    sqliteFree(zCol);
    return 0;
  }

  /*

  }

lookupname_end:
  /* Clean up and return
  */
  sqliteFree(zDb);
  sqliteFree(zTab);

  sqlite3ExprDelete(pExpr->pLeft);
  pExpr->pLeft = 0;
  sqlite3ExprDelete(pExpr->pRight);
  pExpr->pRight = 0;
  pExpr->op = TK_COLUMN;
lookupname_end_2:
  sqliteFree(zCol);
  if( cnt==1 ){
    assert( pNC!=0 );
    sqlite3AuthRead(pParse, pExpr, pNC->pSrcList);
    if( pMatch && !pMatch->pSelect ){
      pExpr->pTab = pMatch->pTab;
    }
    /* Increment the nRef value on all name contexts from TopNC up to
    ** the point where the name matched. */
    for(;;){
      assert( pTopNC!=0 );
      pTopNC->nRef++;
      if( pTopNC==pNC ) break;
      pTopNC = pTopNC->pNext;
    }
    return 0;
  } else {
    return 1;
  }
}

/*
** pExpr is a node that defines a function of some kind.  It might
** be a syntactic function like "count(x)" or it might be a function
** that implements an operator, like "a LIKE b".  
**

# 2005 January 19
#
# 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 testing correlated subqueries
#
# $Id: subquery.test,v 1.9 2005/05/23 15:06:39 drh Exp $
#

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

ifcapable !subquery {
  finish_test

  }
  execsql {INSERT INTO t3 VALUES((SELECT max(a) FROM t3)+1)}
} {}
do_test subquery-4.2.2 {
  execsql {INSERT INTO t3 VALUES((SELECT max(a) FROM t3)+1)}
} {}

#------------------------------------------------------------------
# The subquery-5.* tests make sure string literals in double-quotes
# are handled efficiently.  Double-quote literals are first checked
# to see if they match any column names.  If there is not column name
# match then those literals are used a string constants.  When a
# double-quoted string appears, we want to make sure that the search
# for a matching column name did not cause an otherwise static subquery
# to become a dynamic (correlated) subquery.
#
do_test subquery-5.1 {
  proc callcntproc {n} {
    incr ::callcnt
    return $n
  }
  set callcnt 0
  db function callcnt callcntproc
  execsql {
    CREATE TABLE t4(x,y);
    INSERT INTO t4 VALUES('one',1);
    INSERT INTO t4 VALUES('two',2);
    INSERT INTO t4 VALUES('three',3);
    INSERT INTO t4 VALUES('four',4);
    CREATE TABLE t5(a,b);
    INSERT INTO t5 VALUES(1,11);
    INSERT INTO t5 VALUES(2,22);
    INSERT INTO t5 VALUES(3,33);
    INSERT INTO t5 VALUES(4,44);
    SELECT b FROM t5 WHERE a IN 
       (SELECT callcnt(y)+0 FROM t4 WHERE x="two")
  }
} {22}
do_test subquery-5.2 {
  # This is the key test.  The subquery should have only run once.  If
  # The double-quoted identifier "two" were causing the subquery to be
  # processed as a correlated subquery, then it would have run 4 times.
  set callcnt
} {1}





finish_test