我是Postgres的新手，正在从事我的工作。我不得不创建一个只有1列的表，然后让我在pgadmin III上运行以下语句：

BEGIN;
INSERT INTO mytable VALUES (1);
SAVEPOINT savepoint1;
INSERT INTO mytable VALUES (2);
ROLLBACK TO SAVEPOINT savepoint1;
INSERT INTO mytable VALUES (3);
SAVEPOINT savepoint2;
INSERT INTO mytable VALUES (4);
INSERT INTO mytable VALUES (5);
SAVEPOINT savepoint3;
SELECT * FROM mytable;
--NOTE: You need to run this IF statement as PGScript 
--(button next to the normal run button)
IF (CAST ((SELECT MAX(id) FROM mytable) AS INTEGER) = 4)
BEGIN
      RELEASE SAVEPOINT savepoint2;
END
ELSE
BEGIN
      INSERT INTO mytable VALUES(6);
END
--Run the next steps normally
SAVEPOINT savepoint2;
INSERT INTO mytable VALUES (7);
RELEASE SAVEPOINT savepoint2;
INSERT INTO mytable VALUES (8);
ROLLBACK TO savepoint2;
COMMIT;

当我运行此命令时，出现以下错误：“ IF”或附近的语法错误

我已经看过这个38.6.2。条件句38.6.2。条件句，我对此不太了解，是否需要将查询更改为

IF (CAST ((SELECT MAX(id) FROM mytable) AS INTEGER) = 4) THEN 
BEGiN

然后当它结束时，我应该以：

END IF

为什么毕竟有错误？