A fix (bug #3756: ISNULL(QUOTE()) returns 1 for every row after 1st NULL)

mysql-test/r/func_str.result

@@ -273,3 +273,12 @@ i	ELT(j, '345', '34')
 1	345
 2	34
 DROP TABLE t1;
+create table t1(a char(4));
+insert into t1 values ('one'),(NULL),('two'),('four');
+select a, quote(a), isnull(quote(a)), quote(a) is null, ifnull(quote(a), 'n') from t1;
+a	quote(a)	isnull(quote(a))	quote(a) is null	ifnull(quote(a), 'n')
+one	'one'	0	0	'one'
+NULL	NULL	1	1	n
+two	'two'	0	0	'two'
+four	'four'	0	0	'four'
+drop table t1;

mysql-test/t/func_str.test

@@ -163,3 +163,12 @@ CREATE TABLE t1 (i int, j int);
 INSERT INTO t1 VALUES (1,1),(2,2);
 SELECT DISTINCT i, ELT(j, '345', '34') FROM t1;
 DROP TABLE t1;
+
+#
+# bug #3756: quote and NULL
+#
+
+create table t1(a char(4));
+insert into t1 values ('one'),(NULL),('two'),('four');
+select a, quote(a), isnull(quote(a)), quote(a) is null, ifnull(quote(a), 'n') from t1;
+drop table t1;
\ No newline at end of file

sql/item_strfunc.cc

@@ -2215,6 +2215,7 @@ String *Item_func_quote::val_str(String *str)
   }
   *to= '\'';
   str->length(new_length);
+  null_value= 0;
   return str;
 
 null: