Fix for Bug#34274: Invalid handling of 'DEFAULT 0'

for YEAR data type.

The problem was that for some unknown reason 0 was not allowed
as a default value for YEAR data type. That was coded before BK.
However the Manual does not say a word about such a limitation.
Also, it looks inconsistent with other data types.

The fix is to allow 0 as a default value.


mysql-test/r/create.result:
  Update result file.
mysql-test/t/create.test:
  Add a test case for Bug#34274: Invalid handling of 'DEFAULT 0'
  for YEAR data type.
sql/unireg.cc:
  Allow 0 as a default value for YEAR data type.

mysql-test/t/create.test

@@ -1365,6 +1365,8 @@ create table t1 like information_schema.character_sets;
 show create table t1;
 drop table t1;
 
+###########################################################################
+
 --echo
 --echo # --
 --echo # -- Bug#21380: DEFAULT definition not always transfered by CREATE
@@ -1407,8 +1409,10 @@ DROP TABLE t2;
 
 --echo
 --echo # -- End of test case for Bug#21380.
---echo
 
+###########################################################################
+
+--echo
 --echo # --
 --echo # -- Bug#18834: ALTER TABLE ADD INDEX on table with two timestamp fields
 --echo # --
@@ -1471,6 +1475,50 @@ DROP TABLE t3;
 
 --echo
 --echo # -- End of Bug#18834.
+
+###########################################################################
+
+--echo
+--echo # --
+--echo # -- Bug#34274: Invalid handling of 'DEFAULT 0' for YEAR data type.
+--echo # --
 --echo
 
+--disable_warnings
+DROP TABLE IF EXISTS t1;
+--enable_warnings
+
+--echo
+CREATE TABLE t1(c1 YEAR DEFAULT 2008, c2 YEAR DEFAULT 0);
+
+--echo
+SHOW CREATE TABLE t1;
+
+--echo
+INSERT INTO t1 VALUES();
+
+--echo
+SELECT * FROM t1;
+
+--echo
+ALTER TABLE t1 MODIFY c1 YEAR DEFAULT 0;
+
+--echo
+SHOW CREATE TABLE t1;
+
+--echo
+INSERT INTO t1 VALUES();
+
+--echo
+SELECT * FROM t1;
+
+--echo
+DROP TABLE t1;
+
+--echo
+--echo # -- End of Bug#34274
+
+###########################################################################
+
+--echo
 --echo End of 5.1 tests