SQLite

**    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 UPDATE statements.
**
** $Id: update.c,v 1.48 2002/07/16 17:22:51 drh Exp $
*/
#include "sqliteInt.h"

/*
** Process an UPDATE statement.
*/
void sqliteUpdate(

  for(i=0; i<pTab->nCol; i++) aXRef[i] = -1;

  /* If there are FOR EACH ROW triggers, allocate temp tables */
  if( row_triggers_exist ){
    newIdx = pParse->nTab++;
    oldIdx = pParse->nTab++;
  }

  /* Allocate a cursors for the main database table and for all indices.
  ** The index cursors might not be used, but if they are used they
  ** need to occur right after the database cursor.  So go ahead and
  ** allocate enough space, just in case.
  */
  base = pParse->nTab++;
  for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
    pParse->nTab++;
  }

  /* Resolve the column names in all the expressions in both the
  ** WHERE clause and in the new values.  Also find the column index
  ** for each column to be updated in the pChanges array.
  */

  if( pWhere ){
    if( sqliteExprResolveIds(pParse, base, pTabList, 0, pWhere) ){
      goto update_cleanup;
    }
    if( sqliteExprCheck(pParse, pWhere, 0, 0) ){
      goto update_cleanup;
    }

        break;
      }
    }
  }
  for(i=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, i++){
    if( openAll || aIdxUsed[i] ){
      sqliteVdbeAddOp(v, openOp, base+i+1, pIdx->tnum);
      assert( pParse->nTab>base+i+1 );
    }

  }

  /* Loop over every record that needs updating.  We have to load
  ** the old data for each record to be updated because some columns
  ** might not change and we will need to copy the old value.
  ** Also, the old data is needed to delete the old index entires.
  ** So make the cursor point at the old record.

# 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 UPDATE statement.
#
# $Id: update.test,v 1.10 2002/07/16 17:22:51 drh Exp $

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

# Try to update an non-existent table
#
do_test update-1.1 {

  }
} {1 {constraint failed}}
do_test update-10.10 {
  catchsql {
    SELECT * FROM t1;
  }
} {0 {1 2 3 4 13 6 2 3 4 4 6 7}}

# Make sure we can handle a subquery in the where clause.
#
do_test update-11.1 {
  execsql {
    UPDATE t1 SET e=e+1 WHERE b IN (SELECT b FROM t1);
    SELECT b,e FROM t1;
  }
} {2 14 3 7}
do_test update-11.2 {
  execsql {
    UPDATE t1 SET e=e+1 WHERE a IN (SELECT a FROM t1);
    SELECT a,e FROM t1;
  }
} {1 15 2 8}

finish_test