将这些查询组合成一个返回的函数答案

【问题标题】：Combining these queries into a function that returns将这些查询组合成一个返回的函数
【发布时间】：2019-12-31 18:28:32
【问题描述】：

我有几个查询，我试图将它们组合成一个返回一些值的函数。除了我不知道如何正确地做到这一点。

这是我试图输出的逻辑：

if((SELECT parent_id FROM event_comments WHERE comment_id = $1) == null){

    WITH cte AS (DELETE FROM event_comments WHERE thread_id = '1BZbAR'
    RETURNING parent_id, comment_id, thread_id)
    SELECT parent_id, comment_id, thread_id
    FROM cte
    WHERE parent_id IS NULL;

}else{
    DELETE FROM event_comments WHERE comment_id = $1 AND created_by = $3
    returning parent_id, comment_id, thread_id
}

获取语法错误类型“cte”不存在？

CREATE FUNCTION deleteComment(comment_id integer, created_by UUID, thread_id integer) 
RETURNS cte AS $$

BEGIN
CASE WHEN (SELECT parent_id FROM event_comments WHERE comment_id = $1) is NULL
THEN 
    WITH cte AS (
        DELETE FROM event_comments WHERE thread_id = $3
        RETURNING parent_id, comment_id, thread_id
    )
    SELECT parent_id, comment_id, thread_id
    FROM cte
    WHERE parent_id IS NULL;
ELSE
    WITH cte AS (
        DELETE FROM event_comments WHERE comment_id = $1 AND created_by = $2
        returning parent_id, comment_id, thread_id
    )

END; $$
LANGUAGE plpgsql;

【问题讨论】：

标签： sql postgresql plpgsql

【解决方案1】：

在 plpgsql 函数中，您必须准确指定要返回的内容，cte 不是数据类型，而是您在函数中使用的变量。话虽如此，您应该首先声明要返回的列及其数据类型。如果您愿意，您可以自己创建数据类型，但最简单的方法是返回一个表：

CREATE OR REPLACE FUNCTION 
  deleteComment(comment_id_in INT, created_by_in UUID, thread_id_in INT) 
RETURNS TABLE (parent_id_out INT, comment_id_out INT, thread_id_out INT) AS $$
BEGIN
  IF (SELECT parent_id FROM event_comments WHERE comment_id = $1) IS NULL THEN
    RETURN QUERY DELETE FROM event_comments 
      WHERE thread_id = $3
      RETURNING parent_id, comment_id, thread_id;
  ELSE
    RETURN QUERY DELETE FROM event_comments 
      WHERE comment_id = $1 AND created_by = $2
      RETURNING parent_id, comment_id, thread_id;
  END IF;
END;
$$ LANGUAGE plpgsql;

样本数据：

CREATE TEMPORARY TABLE event_comments 
(comment_id INT, parent_id INT, thread_id INT, created_by UUID);
INSERT INTO event_comments VALUES (1,1,1,'123e4567-e89b-12d3-a456-426655440000');

测试：

SELECT * FROM deleteComment(1,'123e4567-e89b-12d3-a456-426655440000',4);

 parent_id_out | comment_id_out | thread_id_out 
---------------+----------------+---------------
             1 |              1 |             1
(1 Zeile)

查看this answer 以获得更简洁的示例。

【讨论】：