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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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28
src/expr.c
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@@ -12,7 +12,7 @@
** This file contains routines used for analyzing expressions and
** for generating VDBE code that evaluates expressions in SQLite.
**
** $Id: expr.c,v 1.65 2002/05/30 02:35:12 drh Exp $
** $Id: expr.c,v 1.66 2002/05/31 15:51:25 drh Exp $
*/
#include "sqliteInt.h"
@@ -933,9 +933,7 @@ void sqliteExprCode(Parse *pParse, Expr *pExpr){
}
case TK_CASE: {
int expr_end_label;
int null_result_label;
int jumpInst;
int nullBypassInst;
int addr;
int nExpr;
int i;
@@ -945,44 +943,32 @@ void sqliteExprCode(Parse *pParse, Expr *pExpr){
assert(pExpr->pList->nExpr > 0);
nExpr = pExpr->pList->nExpr;
expr_end_label = sqliteVdbeMakeLabel(v);
null_result_label = sqliteVdbeMakeLabel(v);
if( pExpr->pLeft ){
sqliteExprCode(pParse, pExpr->pLeft);
nullBypassInst = sqliteVdbeAddOp(v, OP_IsNull, -1, 0);
}
for(i=0; i<nExpr; i=i+2){
sqliteExprCode(pParse, pExpr->pList->a[i].pExpr);
sqliteVdbeAddOp(v, OP_IsNull, -1, null_result_label);
if( pExpr->pLeft ){
sqliteVdbeAddOp(v, OP_Dup, 1, 1);
jumpInst = sqliteVdbeAddOp(v, OP_Ne, 0, 0);
jumpInst = sqliteVdbeAddOp(v, OP_Ne, 1, 0);
sqliteVdbeAddOp(v, OP_Pop, 1, 0);
}else{
jumpInst = sqliteVdbeAddOp(v, OP_IfNot, 0, 0);
jumpInst = sqliteVdbeAddOp(v, OP_IfNot, 1, 0);
}
sqliteExprCode(pParse, pExpr->pList->a[i+1].pExpr);
sqliteVdbeAddOp(v, OP_Goto, 0, expr_end_label);
if( i>=nExpr-2 ){
sqliteVdbeResolveLabel(v, null_result_label);
sqliteVdbeAddOp(v, OP_Pop, 1, 0);
if( pExpr->pRight!=0 ){
sqliteVdbeAddOp(v, OP_String, 0, 0);
sqliteVdbeAddOp(v, OP_Goto, 0, expr_end_label);
}
}
addr = sqliteVdbeCurrentAddr(v);
sqliteVdbeChangeP2(v, jumpInst, addr);
}
if( pExpr->pLeft ){
sqliteVdbeAddOp(v, OP_Pop, 1, 0);
}
if( pExpr->pRight ){
sqliteExprCode(pParse, pExpr->pRight);
}else{
sqliteVdbeAddOp(v, OP_String, 0, 0);
}
sqliteVdbeResolveLabel(v, expr_end_label);
if( pExpr->pLeft ){
sqliteVdbeAddOp(v, OP_Pull, 1, 0);
sqliteVdbeAddOp(v, OP_Pop, 1, 0);
sqliteVdbeChangeP2(v, nullBypassInst, sqliteVdbeCurrentAddr(v));
}
}
break;
}