170   char *zNull;               /* Text to substitute for an SQL NULL value */  member
564   if( pDb->zNull ){  in DbDeleteCmd()
565     Tcl_Free(pDb->zNull);  in DbDeleteCmd()
982           pVal = Tcl_NewStringObj(p->pDb->zNull, -1);  in tclSqlFunc()
1755       return Tcl_NewStringObj(p->pDb->zNull, -1);  in dbEvalColumnValue()
2446     const char *zNull;  in DbObjCmd()  local
2458       zNull = Tcl_GetStringFromObj(objv[6], 0);  in DbObjCmd()
2460       zNull = "";  in DbObjCmd()
2466     nNull = strlen30(zNull);  in DbObjCmd()
2565         if( (nNull>0 && strcmp(azCol[i], zNull)==0)  in DbObjCmd()
2976       char *zNull = Tcl_GetStringFromObj(objv[2], &len);  in DbObjCmd()  local
2977       if( pDb->zNull ){  in DbObjCmd()
2978         Tcl_Free(pDb->zNull);  in DbObjCmd()
2980       if( zNull && len>0 ){  in DbObjCmd()
2981         pDb->zNull = Tcl_Alloc( len + 1 );  in DbObjCmd()
2982         memcpy(pDb->zNull, zNull, len);  in DbObjCmd()
2983         pDb->zNull[len] = '\0';  in DbObjCmd()
2985         pDb->zNull = 0;  in DbObjCmd()
2988     Tcl_SetObjResult(interp, Tcl_NewStringObj(pDb->zNull, -1));  in DbObjCmd()