170   char *zNull;               /* Text to substitute for an SQL NULL value */  member
575     if( pDb->zNull ){  in delDatabaseRef()
576       Tcl_Free(pDb->zNull);  in delDatabaseRef()
1003           pVal = Tcl_NewStringObj(p->pDb->zNull, -1);  in tclSqlFunc()
1779       return Tcl_NewStringObj(p->pDb->zNull, -1);  in dbEvalColumnValue()
2470     const char *zNull;  in DbObjCmd()  local
2482       zNull = Tcl_GetStringFromObj(objv[6], 0);  in DbObjCmd()
2484       zNull = "";  in DbObjCmd()
2490     nNull = strlen30(zNull);  in DbObjCmd()
2589         if( (nNull>0 && strcmp(azCol[i], zNull)==0)  in DbObjCmd()
3002       char *zNull = Tcl_GetStringFromObj(objv[2], &len);  in DbObjCmd()  local
3003       if( pDb->zNull ){  in DbObjCmd()
3004         Tcl_Free(pDb->zNull);  in DbObjCmd()
3006       if( zNull && len>0 ){  in DbObjCmd()
3007         pDb->zNull = Tcl_Alloc( len + 1 );  in DbObjCmd()
3008         memcpy(pDb->zNull, zNull, len);  in DbObjCmd()
3009         pDb->zNull[len] = '\0';  in DbObjCmd()
3011         pDb->zNull = 0;  in DbObjCmd()
3014     Tcl_SetObjResult(interp, Tcl_NewStringObj(pDb->zNull, -1));  in DbObjCmd()