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Refinements to NULL processing: NULLs are indistinct for DISTINCT and UNION.

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Multiplying a NULL by zero yields zero. In a CASE expression, a NULL comparison
is considered false, not NULL.  With these changes, NULLs in SQLite now work
the same as in PostgreSQL and in Oracle. (CVS 600)

FossilOrigin-Name: da61aa1d238539dff9c43fd9f464d311e28d669f
This commit is contained in:
drh
2002-05-31 15:51:25 +00:00
parent 0f89253e21
commit f570f011eb
11 changed files with 279 additions and 59 deletions
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13
src/select.c
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@@ -12,7 +12,7 @@
** This file contains C code routines that are called by the parser
** to handle SELECT statements in SQLite.
**
** $Id: select.c,v 1.88 2002/05/27 12:24:48 drh Exp $
** $Id: select.c,v 1.89 2002/05/31 15:51:25 drh Exp $
*/
#include "sqliteInt.h"
@@ -326,7 +326,12 @@ static int selectInnerLoop(
** part of the result.
*/
if( distinct>=0 && pEList && pEList->nExpr>0 ){
sqliteVdbeAddOp(v, OP_IsNull, -pEList->nExpr, sqliteVdbeCurrentAddr(v)+7);
/* For the purposes of the DISTINCT keyword to a SELECT, NULLs
** are indistinct. This was confirmed by experiment in Oracle
** and PostgreSQL. It seems contradictory, but it appears to be
** true.
** sqliteVdbeAddOp(v, OP_IsNull, -pEList->nExpr,sqliteVdbeCurrentAddr(v)+7);
*/
sqliteVdbeAddOp(v, OP_MakeKey, pEList->nExpr, 1);
sqliteVdbeAddOp(v, OP_Distinct, distinct, sqliteVdbeCurrentAddr(v)+3);
sqliteVdbeAddOp(v, OP_Pop, pEList->nExpr+1, 0);
@@ -358,7 +363,7 @@ static int selectInnerLoop(
** table iParm.
*/
if( eDest==SRT_Union ){
sqliteVdbeAddOp(v, OP_MakeRecord, nColumn, 1);
sqliteVdbeAddOp(v, OP_MakeRecord, nColumn, 0);
sqliteVdbeAddOp(v, OP_String, 0, 0);
sqliteVdbeAddOp(v, OP_PutStrKey, iParm, 0);
}else
@@ -377,7 +382,7 @@ static int selectInnerLoop(
** the temporary table iParm.
*/
if( eDest==SRT_Except ){
int addr = sqliteVdbeAddOp(v, OP_MakeRecord, nColumn, 1);
int addr = sqliteVdbeAddOp(v, OP_MakeRecord, nColumn, 0);
sqliteVdbeAddOp(v, OP_NotFound, iParm, addr+3);
sqliteVdbeAddOp(v, OP_Delete, iParm, 0);
}else