PostgreSQL 函数返回一个表

Question

我需要创建一个函数来计算每个分支的帐户总和并进行比较 到分支余额。

我尝试过这样做：

CREATE OR REPLACE FUNCTION t3() RETURNS TABLE(bb integer, sum integer) AS $$ 
BEGIN
FOR i IN 1..50 LOOP
BEGIN
SELECT bbalance FROM branch WHERE branchid = i
union
SELECT  sum(balance) FROM account WHERE branch = i;
END;
END LOOP;
END;
$$ LANGUAGE plpgsql;

我现在有点困惑......我希望它返回一个包含 2 列的表：一个具有分支中 bbalance 的值；第二个是该分支中每个余额的总和。

我需要一些可以用select * from t3() 打电话的东西。

这就是我在 pgAdmin 查询编辑器中写的：

CREATE OR REPLACE FUNCTION t3() RETURNS TABLE(bb integer, sum integer) AS $$ 
DECLARE
   bal integer;
BEGIN
  FOR i IN SELECT branchid FROM branch
  LOOP
    SELECT INTO bb bbalance FROM branch WHERE branchid = i;
    SELECT INTO "sum" sum(balance) FROM account WHERE branch = i;
    RETURN NEXT;
  END LOOP;
  RETURN;
END;
$$ LANGUAGE plpgsql;

错误是：

ERRORE:  variabile del ciclo sulle righe deve essere una variabile di tipo row o record o una lista di variabili scalari
LINE 5:   FOR i IN SELECT branchid FROM branch
              ^

********** Error **********

ERRORE: variabile del ciclo sulle righe deve essere una variabile di tipo row o record o una lista di variabili scalari
SQL state: 42601
Character: 119

意大利语 - 翻译为：
对行进行循环的循环变量必须是记录或行变量或标量变量列表。

Answer 1

你需要设置表变量而不是RETURN NEXT，例如

CREATE OR REPLACE FUNCTION t3() RETURNS TABLE(bb integer, sum integer) AS $$ 
DECLARE
   i integer;
BEGIN
  FOR i IN SELECT branchid FROM branch
  LOOP
    SELECT INTO bb bbalance FROM branch WHERE branchid = i;
    SELECT INTO "sum" sum(balance) FROM account WHERE branch = i;
    RETURN NEXT;
  END LOOP;
  RETURN;
END;
$$ LANGUAGE plpgsql;

但实际上，所有这些都可以在没有 PL/PgSQL 的情况下更干净地完成，因为连接上的一个微不足道的 GROUP BY：

SELECT b.branchid, b.bbalance, coalesce(sum(a.balance), 0) AS acctbalance
FROM branch b LEFT OUTER JOIN account a ON (b.branchid = a.branch)
GROUP BY b.branchid;

顺便说一句，“sum”作为参数名称的选择并不好，因为它是一个常用的内置聚合函数。