TSQL - CASE創建兩個列中的一個

Question

對於此簡化的表結構（請參閱fiddle），我需要刪除爲相同ID輸出的第二行。單個ID的行值可能僅爲「1」。

CREATE TABLE lookup 
    (
    id int, 
    field varchar(20), 
    row varchar(20), 
    value varchar(50) 
    ); 

INSERT INTO lookup 
(id,field, row, value) 
VALUES 
(1,'55', '1', '1XYZ'), 
(1,'55', '2', '2XYZ'), 
(2,'55', '1', '3XYZ'); 


CREATE TABLE output 
    (
    id int, 
    value_1 varchar(50), 
    value_2 varchar(50) 
    ); 

INSERT INTO output 
(id, value_1, value_2) 
VALUES 
(1, '1XYZ', '2XYZ'), 
(2, '3XYZ', null); 


-- wrong 
select id 
,case when (field = 55 and row = 1) then value END AS value_1 
,case when (field = 55 and row = 2) then value END AS value_2 
from lookup; 

希望你能告訴我如何。

謝謝。

Answer 1

只需添加聚集到查詢：

select id 
,max(case when (field = 55 and row = 1) then value END) AS value_1 
,max(case when (field = 55 and row = 2) then value END) AS value_2 
from lookup 
group by id; 

Demo here