PostgreSQL - 迭代查询结果

Question

我正在用pgsql脚本语言创建一个函数,在这一点上我想做的是迭代查询的结果,并为每一行做一些特定的事情.我目前的尝试如下,其中temprow声明为temprow user_data.users%rowtype.有问题的代码如下:

FOR temprow IN
        SELECT * FROM user_data.users ORDER BY user_seasonpts DESC LIMIT 10
    LOOP
        SELECT user_id,user_seasonpts INTO player_idd,season_ptss FROM temprow;
        INSERT INTO user_data.leaderboards (season_num,player_id,season_pts) VALUES (old_seasonnum,player_idd,season_ptss);
    END LOOP;  

但是我从这里得到以下错误:ERROR: relation "temprow" does not exist.如果我明白我想要做什么,你能指出我正确的方法吗？

Answer 1

temprow是一个记录变量,它依次绑定到第一个记录SELECT.

所以你应该写:

FOR temprow IN
        SELECT * FROM user_data.users ORDER BY user_seasonpts DESC LIMIT 10
    LOOP
        INSERT INTO user_data.leaderboards (season_num,player_id,season_pts) VALUES (old_seasonnum,temprow.userd_id,temprow.season_ptss);
    END LOOP;

此循环可以进一步简化为单个查询:

INSERT INTO user_data.leaderboards (season_num,player_id,season_pts)
SELECT old_seasonnum,player_idd,season_ptss FROM user_data.users ORDER BY user_seasonpts DESC LIMIT 10

Answer 2

为了将来的参考，我想强调Suchhara对已接受答案的评论

在 Postgres@12 上，以下内容可以工作：

DO $$
DECLARE temprow RECORD;
BEGIN FOR temprow IN
    SELECT * FROM user_data.users ORDER BY user_seasonpts DESC LIMIT 10
  LOOP
    INSERT INTO user_data.leaderboards (season_num,player_id,season_pts) VALUES (old_seasonnum,temprow.userd_id,temprow.season_ptss);
  END LOOP;
END; $$

Answer 3

循环选择并使用循环项值来过滤和计算其他值的函数，

CREATE FUNCTION "UpdateTable"() RETURNS boolean
    LANGUAGE plpgsql
AS
$$
DECLARE
    TABLE_RECORD RECORD;
    BasePrice NUMERIC;
    PlatformFee NUMERIC;
    MarketPrice NUMERIC;
    FinalAmount NUMERIC;
BEGIN
    FOR TABLE_RECORD IN SELECT * FROM "SchemaName1"."TableName1" -- can select required fields only

        LOOP
            SELECT "BasePrice", "PlatformFee" INTO BasePrice, PlatformFee
            FROM "SchemaName2"."TableName2" WHERE "UserID" = TABLE_RECORD."UserRID";

            SELECT "MarketPrice" / 100 INTO MarketPrice FROM "SchemaName3"."TableName3" WHERE "DateTime" = TABLE_RECORD."DateTime";

            FinalAmount = TABLE_RECORD."Qty" * (BasePrice + PlatformFee - MarketPrice);

            UPDATE "SchemaName1"."TableName1" SET "MarketPrice" = MarketPrice, "Amount" = CFDAmount
            WHERE "ID" = CFD_RECORD."ID"; -- can update other schema tables also
        END LOOP;

    RETURN TRUE;
END
$$;