postgresql - postgresql 自定义自增字段(发票/订单号)

Question

基本要求是以以下格式创建订单号:

(M)M-SSS

其中 MM 代表当前月份，SSSS 代表当月的订单顺序。例如，1-002 代表一月份提交的第二个订单。

使用 TRIGGER 我希望自动递增和插入透明地工作。

不幸的是，我已经很久没有接触存储过程了，这是我第一次接触 postgresql。任何指向正确方向的帮助将不胜感激。

更新:这是使用@peterm 代码的最终实现

-- The trigger
CREATE TRIGGER add_order_number 
   BEFORE INSERT ON orders FOR EACH ROW
   EXECUTE PROCEDURE order_number_update();

-- The trigger function
CREATE FUNCTION order_number_update() RETURNS TRIGGER AS $$
DECLARE
    next_order TEXT;
BEGIN
    -- get the next order number
    SELECT INTO next_order CONCAT(CAST(DATE_PART('MONTH', CURRENT_DATE) AS VARCHAR(2)),
       '-', 
       LPAD(CAST(COALESCE(CAST(RIGHT(MAX(order_number), 3) AS INT), 0) + 1 AS VARCHAR(3)), 3, '0'))
    FROM orders
    WHERE CAST(LEFT(order_number, STRPOS(order_number, '-') - 1) AS INT) = DATE_PART('MONTH', CURRENT_DATE);

    -- update the field
    NEW.order_number = next_order;
    RETURN NEW;
END;
$$ LANGUAGE plpgsql;

注意:通过将更新添加为 BEFORE INSERT 触发器，它以完全透明和可预测的方式运行，就像普通的 SERIAL 或 BIGSERIAL 字段一样。

Answer 1

你在找这样的东西吗？

-- Next No calculated for current month
SELECT CONCAT(CAST(DATE_PART('MONTH', CURRENT_DATE) AS VARCHAR(2)),
       '-', 
       LPAD(CAST(COALESCE(CAST(RIGHT(MAX(order_no), 4) AS INT), 0) + 1 AS VARCHAR(4)), 4, '0')) next_no
  FROM orders
 WHERE CAST(LEFT(order_no, STRPOS(order_no, '-') - 1) AS INT) = DATE_PART('MONTH', CURRENT_DATE)
;

输出:

| NEXT_NO |
-----------
|  5-0001 |

假设有一条记录order_no = '1-0001' 那么

-- Next No for January
SELECT CONCAT(CAST(DATE_PART('MONTH', DATE '2013-01-01') AS VARCHAR(2)),
       '-', 
       LPAD(CAST(COALESCE(CAST(RIGHT(MAX(order_no), 4) AS INT), 0) + 1 AS VARCHAR(4)), 4, '0')) next_no
  FROM orders
 WHERE CAST(LEFT(order_no, STRPOS(order_no, '-') - 1) AS INT) = DATE_PART('MONTH', DATE '2013-01-01')
;

输出:

| NEXT_NO |
-----------
|  1-0002 |

SQLFiddle