fix: allow sample and extend as unquoted identifiers

Signed-off-by: 付典 <fudianchn@gmail.com>

Author: fudianchn

src/main/jjtree/net/sf/jsqlparser/parser/JSqlParserCC.jjt

@@ -6863,7 +6863,9 @@ String RelObjectName() :
           | tk=<K_ON> | tk=<K_OPTIMIZE> | tk=<K_ORDER> | tk=<K_PROCEDURE>
           | tk=<K_PUBLIC> | tk=<K_QUALIFY> | tk=<K_RIGHT> | tk=<K_FILE>
           | tk=<K_SET> | tk=<K_SOME> | tk=<K_START> | tk=<K_TABLES>
-          | tk=<K_TOP> | tk=<K_VALUE> | tk=<K_VALUES> )
+          | tk=<K_TOP> | tk=<K_VALUE> | tk=<K_VALUES>
+          | tk=<K_SAMPLE>
+          | tk=<K_EXTEND> )
     )
     { return result != null ? result : tk.image; }
 }

src/test/java/net/sf/jsqlparser/statement/KeywordsTest.java

@@ -62,4 +62,19 @@ public void testGroupsAsIdentifier() throws JSQLParserException {
         assertSqlCanBeParsedAndDeparsed("SELECT a groups FROM mytable", true);
         assertSqlCanBeParsedAndDeparsed("CREATE TABLE mytable (groups INT)", true);
     }
+
+    // sample and extend are non-reserved in the common dialects and reach the
+    // parser as ordinary table and column names in downstream rewriting tools.
+    @Test
+    public void testSampleExtendAsIdentifier() throws JSQLParserException {
+        assertSqlCanBeParsedAndDeparsed("SELECT sample, extend FROM mytable", true);
+        assertSqlCanBeParsedAndDeparsed("SELECT mytable.extend FROM mytable", true);
+        assertSqlCanBeParsedAndDeparsed("SELECT * FROM mytable WHERE extend = 'x'", true);
+        assertSqlCanBeParsedAndDeparsed("UPDATE mytable SET sample = 1, extend = 'x' WHERE id = 1", true);
+        assertSqlCanBeParsedAndDeparsed("INSERT INTO mytable (sample, extend) VALUES (1, 'x')", true);
+        assertSqlCanBeParsedAndDeparsed("SELECT * FROM sample", true);
+        assertSqlCanBeParsedAndDeparsed("DELETE FROM sample WHERE extend = 'x'", true);
+        assertSqlCanBeParsedAndDeparsed("INSERT INTO sample (extend) VALUES ('x')", true);
+        assertSqlCanBeParsedAndDeparsed("SELECT a AS sample, b AS extend FROM mytable", true);
+    }
 }