在 plpgsql 中，我将如何从循环中创建 table 行

Question

我想得到这样的东西：

| month_yr|
+---------+
| 11_2021 |
| 12_2021 |
| 01_2022 |
| 02_2022 |
| 03_2022 |

行数取决于我输入函数的参数，如下所示：

CREATE OR REPLACE FUNCTION
    months_to_avg(qty_months INT)
        RETURNS TABLE(month_yrs TEXT)
        AS $$
            DECLARE
                qty_months INT := 3;
                current_month INT := ( SELECT EXTRACT(MONTH FROM DATE(NOW())) );
                month_col INT;
                current_year INT := ( SELECT EXTRACT(YEAR FROM DATE(NOW())) );
            BEGIN
                FOR month_col IN 1..qty_months LOOP
                    IF current_month < (month_col+1) THEN
                        RETURN CONCAT( ((12+current_month) - month_col), (current_year - 1) ) as month_yr;
                    ELSE
                        RETURN CONCAT( (current_month - month_col), current_year ) as month_yr;
                    END IF;
                END LOOP;
            END
        $$ LANGUAGE plpgsql

但我很难理解如何使用循环 return 这些行。

谢谢！

Answer 1

CREATE OR REPLACE FUNCTION months_to_avg ()
    RETURNS TABLE (
        month_yrs text
    )
    AS $$
DECLARE
    qty_months int := 7;
    current_month int := (
        SELECT
            EXTRACT(MONTH FROM DATE(NOW())));
    month_col int;
    current_year int := (
        SELECT
            EXTRACT(YEAR FROM DATE(NOW())));
BEGIN
    FOR month_col IN 1..qty_months LOOP
        IF month_col > current_month THEN
            RAISE NOTICE 'loop times %', month_col;
            RAISE NOTICE 'current_month - month_col: %, current_year: %', (current_month - month_col + 13), current_year - 1;
            RETURN query
            SELECT
                current_month - month_col + 13 || '_' || current_year - 1;
        ELSE
            RAISE NOTICE 'loop times %', month_col;
            RAISE NOTICE 'current_month - month_col: %, current_year: %', (current_month - month_col), current_year;
            RETURN query
            SELECT
                current_month - month_col + 1 || '_' || current_year;
        END IF;
    END LOOP;
END
$$
LANGUAGE plpgsql;

使用循环，为了正确，使用raise notice/raise 信息将使调试更容易。

在 plpgsql 中，我将如何从循环中创建 table 行

in plpgsql, how would i create table rows from a loop

sql

postgresql

plpgsql