T-SQL несколько строк в столбцах

Question

У меня есть такой набор данных;

data_id  col_id  data_text_value 
----------- ----------- --------------- 
1   1   first first 
1   2   first second 
1   3   first third 
2   2   second second 

Вот запрос объединения для создания набора данных;

select 1 as data_id, 1 as col_id, 'first first' as data_text_value union all 
select 1 as data_id, 2 as col_id, 'first second' as data_text_value union all 
select 1 as data_id, 3 as col_id, 'first third' as data_text_value union all 
select 2 as data_id, 2 as col_id, 'second second' as data_text_value 

Я хочу, чтобы набор данных опрашиваются, чтобы data_id сгруппированы в один ряд со всеми col_id-й в разных столбцах;

with test as (
select 1 as data_id, 1 as col_id, 'first first' as data_text_value union all 
select 1 as data_id, 2 as col_id, 'first second' as data_text_value union all 
select 1 as data_id, 3 as col_id, 'first third' as data_text_value union all 
select 2 as data_id, 2 as col_id, 'second second' as data_text_value 
) 
select 
    distinct test.data_id, 
    cid1_text, 
    cid2_text, 
    cid3_text 
from 
    test 
    left outer join (select data_id, data_text_value as cid1_text from test where col_id=1) cid1 on test.data_id = cid1.data_id 
    left outer join (select data_id, data_text_value as cid2_text from test where col_id=2) cid2 on test.data_id = cid2.data_id 
    left outer join (select data_id, data_text_value as cid3_text from test where col_id=3) cid3 on test.data_id = cid3.data_id 

Какие результаты я хочу;

data_id  col_id  data_text_value 
----------- ----------- --------------- 
1   1   first first 
1   2   first second 
1   3   first third 
2   2   second second 

Но есть способ сделать это так, что если col_id со значением 4 будет включен в таблицу, я хотел бы получить четвертый текстовый столбец без изменения запроса?

Answer 1

Это вы что искали? Он будет работать, даже если вы вставляете больше данных. Ваш стол

with test as (
select 1 as data_id, 1 as col_id, 'first first' as data_text_value union all 
select 1 as data_id, 2 as col_id, 'first second' as data_text_value union all 
select 1 as data_id, 3 as col_id, 'first third' as data_text_value union all 
select 2 as data_id, 2 as col_id, 'second second' as data_text_value 
) 

SELECT * INTO tbl_test 
FROM test 

Фактический запрос

DECLARE @PivotCols VARCHAR(MAX); 

SELECT @PivotCols = COALESCE(@PivotCols + ',','') + QUOTENAME(col_id) 
FROM tbl_test 
GROUP BY col_id 
ORDER BY col_id 

EXEC 
(
'SELECT * 
FROM tbl_test 
PIVOT 
(
    MAX(data_text_value) FOR col_id IN (' + @PivotCols + ') 
) pvt 
' 

Результаты:

data_id  1    2    3 
----------- ------------- ------------- ------------- 
1   first first first second first third 
2   NULL   second second NULL