Postgres中的触发器不直接提供触发器代码，而是调用 trigger函数，该函数可以从任意数量的触发器中调用，尽管通常它们是针对一个特定表上的一个特定事件而定制的.

Triggers in Postgres don't provide trigger code directly, but call a trigger function, which can be called from any number of triggers, though often they are customized for one particular event on one particular table.

触发功能:

CREATE OR REPLACE FUNCTION trg_some_tbl_foo()
  RETURNS trigger AS
$func$
BEGIN

INSERT INTO some_tbl(key, name, describe)   -- or some_other_tbl?
VALUES (OLD.key, OLD.name, OLD.describe);

RETURN OLD;

END
$func$ LANGUAGE plpgsql 

触发器:

CREATE TRIGGER foo         -- not:  "CREATE OR REPLACE" !
AFTER UPDATE OR DELETE ON some_tbl
FOR EACH ROW EXECUTE PROCEDURE trg_some_tbl_foo()

• 为它添加一个 AFTER 触发器以简化操作. BEFORE 触发器必须进行 RETURN NEW 才能使更新生效，但是 NEW 在 DELETE 触发器中不可见.因此，您需要 IF TG_OP = ... 等.

  • Make it an AFTER trigger to simplify. A BEFORE trigger would have to RETURN NEW to make updates work, but NEW is not visible in a DELETE trigger. So you'd need IF TG_OP = ... etc.

    始终为持久化的 INSERT 语句提供目标列表.在Oracle触发器中也是如此.

    Always provide a target list for persisted INSERT statements. This is just as bad in an Oracle trigger.

    您可能有一个带有 serial 列的表.只是不要在插入内容中提及它，序列中的下一个ID会自动插入.

    You probably have a table with a serial column. Just don't mention it in the insert, the next id from the sequence is inserted automatically.

    SO上有许多代码示例.

    There are numerous code examples here on SO.