Question

我刚刚开始使用EVE静态转储，这只是很多关于游戏数据的表格，例如太阳系连接的列表，这就是我正在处理的内容。我想创建一个允许您过滤掉系统的网页，第一步是获取附近的系统列表，并与它们保持距离。

我找到了一个为MSSQL执行此操作的脚本

--By Joanna Davaham http://forum.eveuniversity.org/viewtopic.php?t=44601&p=396107#p424943
--set values
DECLARE @jumpsAway INT =10
DECLARE @MiddleSystemName VARCHAR(50) = 'Aldrat'
DECLARE @Level INT =1

IF OBJECT_ID('tempdb..#map') IS NOT NULL
    DROP TABLE #map

CREATE TABLE #map
(fromSolarSystemID INT, toSolarSystemID INT, Level INT)



INSERT INTO #map
SELECT -1, mSS.solarSystemID, 0 FROM mapSolarSystems mSS
WHERE mSS.solarSystemName= @MiddleSystemName

WHILE @Level <= @jumpsAway
BEGIN


INSERT INTO #map
SELECT mSSJ.fromSolarSystemID, mSSJ.toSolarSystemID, @Level FROM mapSolarSystemJumps mSSJ
WHERE mSSJ.fromSolarSystemID IN (SELECT toSolarSystemID FROM #map WHERE Level = @Level-1)
AND  mSSJ.fromSolarSystemID NOT IN (SELECT fromSolarSystemID FROM #map)


SET @Level=@Level+1
END


SELECT m.*, mSS.solarSystemName, mSS.security  FROM #map m
JOIN mapSolarSystems mSS ON m.toSolarSystemID=mSS.solarSystemID
--WHERE mSS.security<0.45  --uncomment to check all nearby lowsec system

我知道我可能只是使用转储的MSSQL版本，但我也想了解更多关于如何更好地使用PostgreSQL的信息。

我理解它正在做什么以及一切，但我只是不太了解PL / pgSQL以使其工作。

我的尝试是

CREATE FUNCTION near(VARCHAR, INTEGER) RETURNS TABLE(fromID INT,toID INT,jumps INT,name VARCHAR,security VARCHAR) AS $$
DECLARE --Declaration from here http://www.postgresql.org/docs/9.1/static/plpgsql-declarations.html
    MiddleSystemName ALIAS FOR $1;
    jumpsAway ALIAS FOR $2;
    jumps INTEGER :=1;
BEGIN

    --http://stackoverflow.com/questions/11979154/select-into-to-create-a-table-in-pl-pgsql
    CREATE TEMP TABLE map AS
        SELECT -1, mSS.solarSystemID, 0
        FROM mapSolarSystems mSS
        WHERE mSS.solarSystemName= MiddleSystemName;

    LOOP

        --http://www.postgresql.org/docs/9.1/static/plpgsql-statements.html#PLPGSQL-STATEMENTS-EXECUTING-DYN
        --If you don't do it with execute, you can only do one row, I guess?
        EXECUTE 'SELECT
       ||        mSSJ.fromSolarSystemID,
       ||        mSSJ.toSolarSystemID,
       ||        $1
       ||    FROM
       ||        mapSolarSystemJumps mSSJ
       ||    WHERE
       ||        mSSJ.fromSolarSystemID EXISTS (SELECT toSolarSystemID FROM map WHERE jumps = $1 - 1)
       ||        AND mSSJ.fromSolarSystemID NOT EXISTS (SELECT fromSolarSystemID FROM map)'
        INTO map
        USING jumps;



        jumps := jumps + 1
        EXIT WHEN jumps > jumpsAway;
    END LOOP;
    RETURN QUERY SELECT m.*,mSS.solarSystemName, mSS.security FROM JOIN mapSolarSystems mSS ON m.toSolarSystemID = mSS.solarSystemID;
END;
$$ LANGUAGE plpgsql;

产生的错误是

Error is
ERROR:  "map" is not a known variable
LINE 27:         INTO map
                      ^

感谢您的帮助。

Answer 1

PL / pgSQL的

这应该是对plpgsql的有效翻译：

CREATE OR REPLACE FUNCTION f_near(_middlesystemname text, _jumpsaway int)
  RETURNS TABLE(fromid int, toid int, jumps int, name text, security text) AS
$func$
DECLARE
    _jumps integer;
BEGIN

CREATE TEMP TABLE map AS
SELECT -1 AS "fromSolarSystemID"
      ,m."solarSystemID" AS "toSolarSystemID"
      ,0 AS level
FROM   "mapSolarSystems" m
WHERE  "solarSystemName" = _middlesystemname;

-- potentially add indexes on the temp table and ANALYZE if it gets big

FOR _jumps IN 1 .. _jumpsaway LOOP
    INSERT INTO map ("fromSolarSystemID", "toSolarSystemID", level)
    SELECT sj."fromSolarSystemID", sj."toSolarSystemID", _jumps AS level
    FROM   "mapSolarSystemJumps" sj
    JOIN   map m ON  m."toSolarSystemID" = sj."fromSolarSystemID"
                 AND m."level" = _jumps - 1
    LEFT   JOIN map mx ON mx."fromSolarSystemID" = sj."fromSolarSystemID"
    WHERE  mx."fromSolarSystemID" IS NULL;
END LOOP;

RETURN QUERY
SELECT m.*, s."solarSystemName", s."security"
FROM   map m
JOIN   "mapSolarSystems" s ON m."toSolarSystemID" = s."solarSystemID";

END
$func$ LANGUAGE plpgsql;

RECURSIVE CTE - 似乎不起作用

这个带有递归CTE 的简短SQL查询应该已经完成了：

WITH RECURSIVE map AS (
    SELECT -1 AS fromsolarsystemid, m.solarsystemid, 0 AS level
    FROM   mapsolarsystems m
    WHERE  m.solarsystemname = from_id

    UNION  ALL
    SELECT sj.fromsolarsystemid, sj.tosolarsystemid, level + 1
    FROM   mapsolarsystemjumps sj 
    JOIN   map m USING (level)
    LEFT   JOIN map mx USING (fromsolarsystemid)
    WHERE  sj.fromsolarsystemid = m.tosolarsystemid
    AND    mx.fromsolarsystemid IS NULL
    AND    m.level < 10                      -- jumpsAway
    )
SELECT m.*, s.solarsystemname, s.security
FROM   map m
JOIN   mapsolarsystems s ON m.tosolarsystemid = s.solarsystemid
-- WHERE s.security < 0.45  -- uncomment to check all nearby lowsec system

但是：

ERROR:  recursive reference to query "map" must not appear within an outer join
LINE 9:     LEFT   JOIN map mx USING (fromsolarsystemid)

将脚本从MSSQL转换为PL / pgSQL

1 个答案:

PL / pgSQL的

RECURSIVE CTE - 似乎不起作用