Question

我在SQL Server中具有以下数据：

数据创建：

-- First we create some test data.
CREATE TABLE E
(
     [Epinum] VARCHAR(9), 
     [RTyp] VARCHAR(120), 
     [Date] DATETIME
);
GO

INSERT INTO E ([Epinum], [RTyp], [Date])
VALUES ('1', '', CONVERT(datetime, '2002-11-26 14:18:00', 20)),
       ('2', '', CONVERT(datetime, '2002-11-24 15:15:00', 20)),
       ('3', '', CONVERT(datetime, '2002-12-17 11:12:00', 20)),
       ('4', '', CONVERT(datetime, '2002-12-09 19:57:00', 20)),
       ('5', '', CONVERT(datetime, '2002-12-11 06:00:00', 20)),
       ('6', '', CONVERT(datetime, '2002-12-19 12:31:00', 20)),
       ('7', '', CONVERT(datetime, '2002-12-15 08:39:00', 20)),
       ('8', '', CONVERT(datetime, '2002-12-20 08:39:00', 20)),
       ('9', '', CONVERT(datetime, '2002-12-13 08:39:00', 20)),
       ('10', '', CONVERT(datetime, '2002-12-16 08:39:00', 20)),
       ('11', '', CONVERT(datetime, '2002-12-14 08:39:00', 20));
GO

CREATE TABLE UJ
(
    [Epinum] VARCHAR(9), 
    [RTyp] VARCHAR(3)
);
GO

INSERT INTO UJ ([Epinum], [RTyp])
VALUES ('1', '111'), ('1', '222'), ('1', '333'), ('1', '444'),
       ('2', '111'),
       ('3', '111'), ('3', '222'), ('3', '333'),
       ('4', '111'),
       ('5', '111'), ('5', '222'), ('5', '333'), ('5', '444'), 
       ('5', '555'), ('5', '666'), ('5', '777'), ('5', '888'),
       ('7', '111'),
       ('8', '111'),
       ('9', '111'), ('9', '222');
GO

T-SQL查询：

-- Now build a query that will create the data we want. 
;WITH Tmp AS
(
    SELECT 
        *, 
        ROW_NUMBER() OVER (PARTITION BY Epinum ORDER BY Epinum) AS rownum
    FROM 
        UJ 
) 
SELECT DISTINCT 
    Epinum, 
    (SELECT 
         RTyp + CASE 
                   WHEN t.rownum = (SELECT MAX(rownum) FROM Tmp WHERE Epinum = s.Epinum) 
                      THEN '' 
                      ELSE '|' 
                END 
     FROM Tmp AS t
     WHERE t.Epinum = s.Epinum 
     FOR XML PATH(''), TYPE).value('(.)[1]', 'VARCHAR(MAX)') AS Piped 
FROM 
    Tmp AS s;
GO

-- Great. Now we update the E table, joining on Epinum. 
;WITH Tmp AS
(
    SELECT 
        *, ROW_NUMBER() OVER (PARTITION BY Epinum ORDER BY Epinum) AS rownum
    FROM
        UJ 
) 
UPDATE E
SET e.RTyp = q.Piped 
FROM 
    (SELECT DISTINCT 
         Epinum, 
         (SELECT RTyp + CASE 
                           WHEN t.rownum = (SELECT MAX(rownum) FROM Tmp WHERE Epinum = s.Epinum) 
                              THEN '' 
                              ELSE '|' 
                        END 
          FROM Tmp AS t
          WHERE t.Epinum = s.Epinum 
          FOR XML PATH(''), TYPE).value('(.)[1]', 'VARCHAR(MAX)') AS Piped 
      FROM 
          Tmp AS s) AS q 
INNER JOIN 
    E AS e ON q.Epinum = e.Epinum;
GO

这将获取特定Epinum的所有RTyp列，然后用管道对它们进行定界并更新表E中的RTyp。这很好，但是问题是，生产中的表E为〜230万行，UJ为〜900k （都具有更多的列），并且此查询花费的时间太长，无法执行更新。

如何使查询效率更高？

Answer 1

如果您使用的是最新版本的SQL Server，则可以尝试STRING_AGG

SELECT Epinum, STRING_AGG(Rtyp, '|')  delimited
FROM uj
GROUP BY Epinum;

Answer 2

UPDATE E 
SET e.RTyp = q.Piped 
FROM (
    SELECT Epinum, Piped = STUFF(
        (SELECT '|' + RTyp 
         FROM UJ 
         WHERE Epinum = t.Epinum 
         FOR XML PATH ('')), 1, 1, '') 
    FROM UJ AS t 
    GROUP BY Epinum) AS q INNER JOIN E AS e 
        ON q.Epinum = e.Epinum;
GO

SQL Server CTE查询-行到单个定界字符串字段

2 个答案: