如何在SQL中查找对

Question

I have a table containing original records and cancelled records. The original records are marked with code=1 and the cancelled ones are marked with code=2. There are other types of codes as well. I need to find all the original records that do not have a cancellation record in the table.

Eg Table1

id | column2 | column3 | code
-- |-------- | ------- | ---
 1 | abc     | def     | 1
 2 | xyz     | pqr     | 1
 3 | abc     | def     | 2

The result of the query should be the row with id 2 as it has not been cancelled.

I am trying to use self-join

select * 
from table1 t1
 join table1 t2 on t1.column1=t2.column1
               and t1.column2=t2.column2
               and t1.code<t2.code
where not (t1.code=1 and t2.code=2)

Answer 1

SELECT  *
FROM    table1 AS t1
WHERE   code = 1
        AND NOT EXISTS ( SELECT *
                         FROM   table1 t2
                         WHERE  t2.code = 2
                                AND t2.column2 = t1.column2
                                AND t2.column3 = t1.column3 )

Answer 2

This answer is preferable to using NOT EXISTS becauese it avoids a correlated subquery. It also uses joins, which means it can take advantage of indices.

SELECT t1.id,
       t1.column2,
       t1.column3,
       t1.code
FROM table1 t1
INNER JOIN
(
    SELECT column2,
           column3
    FROM table1
    GROUP BY column2,
             column3
    HAVING SUM(CASE WHEN code = 2 THEN 1 ELSE 0 END) = 0
) t2
    ON t1.column2 = t2.column2 AND
       t1.column3 = t2.column3

Answer 3

You can use CTE. Find sum of code as it is integer. If it is greater than 1, it means somewhere for this value there is 2.

;WITH CTE AS
(
    Select column1,column3 from Table1
    GROUP BY column1,column3
    HAVING SUM(code)=1
)

SELECT t.id,CTE.* FROM CTE
INNER JOIN @temp t ON t.column1=CTE.column1 AND t.column3=CTE.column3

Please let me know if it helps.