Fix JOIN clause to reference the correct table in SQL query generation

Author: treyfel

wayang-platforms/wayang-jdbc-template/src/main/java/org/apache/wayang/jdbc/operators/JdbcJoinOperator.java

@@ -73,7 +73,7 @@ public String createSqlClause(Connection connection, FunctionCompiler compiler)
         final String rightTableName = right.field0;
         final String rightKey = right.field1;
 
-        return "JOIN " + leftTableName + " ON " +
+        return "JOIN " + rightTableName + " ON " +
             rightTableName + "." + rightKey
             + "=" + leftTableName + "." + leftKey;
     }

wayang-platforms/wayang-jdbc-template/src/test/java/org/apache/wayang/jdbc/operators/JdbcJoinOperatorTest.java

@@ -119,7 +119,7 @@ void testWithHsqldb() throws SQLException {
         System.out.println();
 
         assertEquals(
-            "SELECT * FROM testA JOIN testA ON testB.a=testA.a;",
+            "SELECT * FROM testA JOIN testB ON testB.a=testA.a;",
             sqlQueryChannelInstance.getSqlQuery()
         );
     }