PostgreSQL函数

Question

我已经创建了此函数来对BOM表（bomitem）上的序号重新排序。

CREATE OR REPLACE FUNCTION seqincr(integer) 
    RETURNS SETOF bomitem AS 
$BODY$ 
DECLARE 
    pItemid ALIAS FOR $1; 
    _row bomitem%ROWTYPE; 
    seqint int; 
    _id int; 


BEGIN 
    seqint=8; 
    FOR _row IN SELECT * 
      FROM bomitem 
      WHERE ((bomitem_parent_item_id=pItemid)) 
    LOOP 
    RETURN NEXT _row; 
    _id = _row.bomitem_id; 
    seqint = seqint+2; 
    update bomitem set bomitem_seqnumber = seqint where bomitem_id=_id; 
    END LOOP; 

    RETURN; 
END; 
$BODY$ 
    LANGUAGE plpgsql VOLATILE 
    COST 100 
    ROWS 1000; 
ALTER FUNCTION seqincr(integer) 
    OWNER TO admin; 

的例子适用于个人bomitem_parent_item_id象下面这样：

SELECT * from seqincr(14917); 

我想改写这个功能遍历

SELECT distinct bomitem_parent_item_id FROM bomitem; 

，使其resequences整个BOM表。

Answer 1

你所要做的是与CTE更加简单：

WITH x AS (
    SELECT bomitem_parent_item_id 
     , row_number() OVER (ORDER BY bomitem_parent_item_id) AS rn 
    FROM bomitem 
    GROUP BY bomitem_parent_item_id 
    ORDER BY bomitem_parent_item_id 
    ) 
UPDATE bomitem b 
SET bomitem_seqnumber = 8 + 2 * rn 
FROM x 
WHERE x.bomitem_parent_item_id = b.bomitem_id; 

你至少需要的PostgreSQL 9.1为data-modifying CTE。

或者使用子查询，在早期版本的，太：

UPDATE bomitem b 
SET bomitem_seqnumber = 8 + 2 * rn 
FROM (
    SELECT bomitem_parent_item_id 
     , row_number() OVER (ORDER BY bomitem_parent_item_id) AS rn 
    FROM bomitem 
    GROUP BY bomitem_parent_item_id 
    ORDER BY bomitem_parent_item_id 
    ) x 
WHERE x.bomitem_parent_item_id = b.bomitem_id; 

但是，你至少需要的PostgreSQL 8.4为window functionrow_number()。