无法使用语句DB（postgres）-Java执行DDL

我需要通过更新数据库（新表、字段和键）来生成DDL语句

但只有当我尝试添加带有外键的表和通过添加外键来修改表时，get error才起作用，但应用程序会无限期地暂停

例如：

instanceStatement.execute ("ALTER TABLE pay ADD CONSTRAINT foranea_pay_customer FOREIGN KEY (customerid) REFERENCES customer (customerid) ON UPDATE CASCADE ON DELETE SET NULL;");

请帮忙。

更改表格
ALTER TABLE
  ADD CONSTRAINT pay foranea_pay_customer -- <<-- one token too many here
   FOREIGN KEY (customerid)
    REFERENCES customer (customerid)
     ON UPDATE CASCADE ON DELETE SET NULL
  ;

为Nea_pay_客户添加约束付款--
ALTER TABLE pay -- <<-- maybe here ???
  ADD CONSTRAINT foranea_pay_customer
   FOREIGN KEY (customerid)
    REFERENCES customer (customerid)
     ON UPDATE CASCADE ON DELETE SET NULL
  ;