Fix for BUG#13067 "JOIN ... USING is case sensitive".

mysql-test/r/select.result:
  Test for BUG#13067
mysql-test/t/select.test:
  Test for BUG#13067
sql/sql_base.cc:
  Correctly compare field names with respect to case sensitivity.

mysql-test/r/select.result

@@ -2912,3 +2912,13 @@ ERROR 23000: Column 'id' in from clause is ambiguous
 SELECT id,t3.id FROM (t1 JOIN t2 ON (t2.id=t1.id)) LEFT JOIN t3 USING (id);
 ERROR 23000: Column 'id' in from clause is ambiguous
 drop table t1, t2, t3;
+create table t1 (a int(10),b int(10));
+create table t2 (a int(10),b int(10));
+insert into t1 values (1,10),(2,20),(3,30);
+insert into t2 values (1,10);
+select * from t1 inner join t2 using (A);
+a	b	b
+1	10	10
+select * from t1 inner join t2 using (a);
+a	b	b
+1	10	10

mysql-test/t/select.test

@@ -2487,3 +2487,15 @@ SELECT id,t3.id FROM t1 JOIN t2 ON (t2.id=t1.id) LEFT JOIN t3 USING (id);
 SELECT id,t3.id FROM (t1 JOIN t2 ON (t2.id=t1.id)) LEFT JOIN t3 USING (id);
 
 drop table t1, t2, t3;
+
+#
+# Bug #13067 JOIN xxx USING is case sensitive
+#
+
+create table t1 (a int(10),b int(10));
+create table t2 (a int(10),b int(10));
+insert into t1 values (1,10),(2,20),(3,30);
+insert into t2 values (1,10);
+# both queries should produce the same result
+select * from t1 inner join t2 using (A);
+select * from t1 inner join t2 using (a);

sql/sql_base.cc

@@ -3414,7 +3414,7 @@ test_if_string_in_list(const char *find, List<String> *str_list)
   {
     if (find_length != curr_str->length())
       continue;
-    if (!strncmp(find, curr_str->ptr(), find_length))
+    if (!my_strcasecmp(system_charset_info, find, curr_str->ptr()))
       return TRUE;
   }
   return FALSE;