sql - 连接两列记录以获得聚合的第三列

Question

我有两列，column1 和 2，每列有 10 条记录，例如：

Column1 (A, A, A, B, B, B, B, C, C, D) 和 Column2 (1, 1, 2, 3, 3, 2, 1, 4, 4, 1)

我需要用这两列创建第三列 column3，使得 column3= (A_1_1_2, B_3_3_2_1, C_4_4, D_1)

请帮助我如何做到这一点，我正在使用 group by 语句和 concatinations 但无法弄清楚如何。

Answer 1

尝试这个：

DECLARE @T TABLE([col1] VARCHAR(1), [col2] VARCHAR(1));

INSERT INTO @T ([col1], [col2])
VALUES 
('A','1'), ('A','1'), ('A','2'), 
('B','3'), ('B','3'), ('B','2'), 
('B','1'), ('C','4'), ('C','4'), ('D','1');

DECLARE @col1 VARCHAR(1), @col2 VARCHAR(1), @CONCAT VARCHAR(MAX);

DECLARE col1_cursor CURSOR
FOR
SELECT DISTINCT col1
FROM @T;

OPEN col1_cursor;

FETCH NEXT
FROM col1_cursor
INTO @col1;


WHILE @@FETCH_STATUS = 0
BEGIN
    SET @CONCAT = ''

    DECLARE col2_cursor CURSOR
    FOR
    SELECT col2
    FROM @T
    WHERE col1 = @col1;

    OPEN col2_cursor;

    FETCH NEXT
    FROM col2_cursor
    INTO @col2;


    WHILE @@FETCH_STATUS = 0
    BEGIN

        IF (@CONCAT = '')
        BEGIN
            SET @CONCAT = @col1 + '-' + @col2;
        END
        ELSE
        BEGIN
            SET @CONCAT = @CONCAT + '-' + @col2
        END


        FETCH NEXT
        FROM col2_cursor
        INTO @col2;
    END

    PRINT @CONCAT

    CLOSE col2_cursor;

    DEALLOCATE col2_cursor;


    FETCH NEXT
    FROM col1_cursor
    INTO @col1;

END

CLOSE col1_cursor;

DEALLOCATE col1_cursor;
GO

Answer 2

干得好。您需要保留第 3 列，并且仅在每个 Col1 组的最后一次观察中输出：

data test;
input Col1 $ Col2;
datalines;
A 1
A 1
A 2
B 3
B 3
B 2
B 1
C 4
C 4
D 1
;;
run;

data test_out;
set test;
by Col1;
format Col3 $64.;
retain Col3;
if first.Col1 then
    Col3 = strip(Col1);

Col3 = catx("_",col3,col2);

if last.Col1 then
    output;
run;

Answer 3

我的大部分答案都使用了在上一个问题中找到的工作。

CREATE TABLE MyTable (COLUMN1 char(1) NULL, COLUMN2 char(1) NULL);

INSERT INTO MyTable VALUES ('A', '1'), ('A', '1'), 
('A', '2'), ('B', '3'), ('B', '3'), ('B', '2'), 
('B', '1'), ('C', '4'), ('C', '4'), ('D', '1');

SELECT COLUMN1 + COLUMN2 AS COLUMN3
FROM(
  SELECT DISTINCT a.COLUMN1,
    (SELECT '_' + b.COLUMN2
     FROM MyTable b
     WHERE a.COLUMN1 = b.COLUMN1
     ORDER BY b.COLUMN1
     FOR XML PATH ('')) AS COLUMN2
  FROM MyTable a
  )c

演示

希望这能让您达到可以修改查询以满足您的需求的程度。

另外，这种方法能够避免可怕的光标。