SQL中如果列中的值大于1，则多次返回一行数据

Question

I have a table of data which is shown below:

I need to select all the data back but if the 'Entries' Column is greater than 1 then it should show that many times in my results.

I am unsure on how or even if this is possible to do, could someone please steer me in the right direction?

The results should look like the below:

Answer 1

One simple method uses a recursive CTE:

with cte as (
      select id, entries, date, postcode, 1 as n
      from t
      union all
      select id, entries, date, postcode, n + 1
      from cte
      where n <= entries
     )
select id, entries, date, postcode
from cte;

Note: If entries could be larger than 100, you need to add option (maxrecursion 0) .

Answer 2

One option joins the table with a list of numbers:

select t.*
from mytable t
inner join (
    select 1 n union select 2 union all select 3 union all select 4 union all select 5
) x on x.n <= t.entries

This query would handle up to 5 repeatition for each records. If you need to handle more, then you can either:

• for a few more records, you can just expand the derived table with more numbers
• generate a table of numbers on the fly by using row_number() against a large table
• create a table of numbers ; this is much more scalable than a hardcoded derived table, and performance will be better than when generating the table on the fly (or running a recursive CTE)

Answer 3

You have tagged with T-SQL, a simple and recursion free way would be to use Cross Apply. ie:

DECLARE @f TABLE (id INT, Entries INT, [Date] DATE, postcode VARCHAR(10));
INSERT INTO @f
(id,Entries,Date,postcode)
VALUES
(1,2,'20191217','SG14LJ'),
(2,2,'20191217','SG14LJ'),
(3,1,'20191217','SG14LJ'),
(4,1,'20191217','SG14LJ'),
(5,1,'20191217','SG14LJ'),
(6,1,'20191217','SG14LJ'),
(7,1,'20191217','SG14LJ'),
(8,1,'20191217','SG14LJ'),
(9,2,'20191217','SG14LJ'),
(10,3,'20191217','SG14LJ');

WITH cteTally AS
(
    SELECT TOP (SELECT MAX(entries) FROM @f)
        ROW_NUMBER() OVER (ORDER BY t1.Object_ID) AS N
        FROM Master.sys.All_Columns t1
        CROSS JOIN Master.sys.All_Columns t2
)
SELECT f.* 
FROM @f f
CROSS APPLY (SELECT TOP(f.Entries) N FROM cteTally) t(n);