在 PL/pgSQL 函数中拆分逗号分隔的字符串 [英] Splitting comma separated string in PL/pgSQL function

问题描述

我正在尝试编写一个函数，该函数将 ID 作为输入并更新该给定 ID 上的某些字段.到目前为止，它看起来像这样:

I am trying to write a function that takes an ID as an input and update some fields on that given ID. So far, it looks like this:

CREATE FUNCTION update_status(p_id character varying,
                              p_status character varying DEFAULT NULL::character varying) RETURNS character varying
    LANGUAGE plpgsql
AS
$$
DECLARE
    v_row_count bigint DEFAULT 0;
    v_result    varchar(255);
BEGIN
    
    IF p_id IS NOT NULL THEN
        SELECT count(user_id)
        INTO v_row_count
        FROM test
        WHERE user_id = p_id;
    END IF;

    IF v_row_count <= 0 THEN
        v_result = 'User not found';
        RETURN v_result;

    ELSE
        IF p_id NOT LIKE '%,%' THEN
            UPDATE test
            SET status     = p_status,
                updated_by = 'admin'
            WHERE user_id IN (p_id);
        ELSE
            --Here comes split and pass multiple IDs into an IN() operator
        END IF;
    END IF;
    
END
$$;

ALTER FUNCTION update_status(varchar, varchar) OWNER TO postgres;

现在，它应该一次只接受一个 ID，但我想知道我是否可以通过将单个字符串拆分为一个 ID 数组(如果它有逗号)来接受多个 ID(甚至可能是数百个)一次分隔符，然后将它们传递给 IN() 运算符.如何将字符串拆分为数组，以便将其提供给 IN() 运算符?

Now, it is supposed to accept only one ID at a time but I wonder if I can get it to also accept multiple IDs -maybe even hundreds- once by splitting that single string into an array of IDs if it has a comma delimiter, then pass those to an IN() operator. How can I get split a string into an array so I can feed it to an IN() operator?

推荐答案

蓝星已经提到有一个内置函数可以将逗号分隔的字符串转换为数组.

Blue Star already mentioned that there is a built-in function to convert a comma separated string into an array.

但我建议不要以逗号分隔的字符串开头.如果要传递可变数量的 ID，请使用 variadic 参数.

But I would suggest to not pass a comma separated string to begin with. If you want to pass a variable number of IDs use a variadic parameter.

你也不需要先运行一个SELECT，你可以在UPDATE语句之后询问系统更新了多少行.

You also don't need to first run a SELECT, you can ask the system how many rows were updated after the UPDATE statement.

CREATE FUNCTION update_status(p_status text, p_id variadic integer[]) 
  RETURNS character varying
  LANGUAGE plpgsql
AS
$$
DECLARE
  v_row_count bigint DEFAULT 0;
BEGIN
  UPDATE test
  SET status     = p_status,
      updated_by = 'admin'
  WHERE user_id = any (p_id);
    
  get diagnostics v_row_count = row_count;
  if v_row_count = 0 then 
    return 'User not found';
  end if;
  
  return concat(v_row_count, ' users updated');
END
$$;

你可以这样使用它:

select update_status('active', 1);
select update_status('active', 5, 8, 42);

---

如果出于某种原因，您拥有"要将其作为单个参数传递，请改用实数组:

---

If for some reason, you "have" to pass this as a single argument, use a real array instead:

CREATE FUNCTION update_status(p_status text, p_id integer[]) 

然后像这样传递它:

select update_status('active', array[5,8,42]);

或

select update_status('active', '{5,8,42}');

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