Question

我有以下功能......

CREATE OR REPLACE FUNCTION class_listing(var_sem integer, var_sy character) RETURNS SETOF RECORD AS
DECLARE
    current_offering record;

BEGIN
    SELECT subcode, offerno INTO current_offering FROM offering WHERE SY=var_sem AND SEM=var_sy;

END;

如何将current_offering作为结果集返回？

Answer 1

您可以使用SQL或PLpgSQL函数。使用匿名记录作为返回类型是不实际的（主要是在编写查询时不友好）。改为使用RETURNS TABLE或OUT参数。

CREATE OR REPLACE FUNCTION class_listing(var_sem integer, var_sy varchar)
RETURNS TABLE (subcode varchar, offerno int) AS $$
BEGIN
  RETURN QUERY SELECT o.subcode, o.offerno
                  FROM offering 
                 WHERE SY=var_sem AND SEM=var_sy;
END;
$$ LANGUAGE plpgsql;

或SQL语言

CREATE OR REPLACE FUNCTION class_listing(var_sem integer, var_sy varchar)
RETURNS TABLE (subcode varchar, offerno int) AS $$
  SELECT o.subcode, o.offerno
                  FROM offering 
                 WHERE SY=$1 AND SEM=$2;
$$ LANGUAGE sql;

注意 - 基于查询的函数作为优化器屏障工作（具有小的例外）。在复杂查询中使用它时要小心。

为了完整性 - 您的示例可以写成：

CREATE OR REPLACE FUNCTION class_listing(var_sem integer, var_sy varchar)
RETURNS SETOF RECORD AS $$
DECLARE current_offering record;
BEGIN
  FOR current_offering IN 
          SELECT o.subcode, o.offerno
             FROM offering 
            WHERE SY=var_sem AND SEM=var_sy;
  LOOP
    RETURN NEXT current_offering;
  END LOOP;
  RETURN;
END;
$$ LANGUAGE plpgsql;

但现在不推荐使用此表单

在pgsql函数中返回ResultSet

1 个答案: