在 MySQL 中只选择偶数/奇数行
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Select only even/odd rows in MySQL
提问by AleVale94
I'm trying to select all even or odd rows from a table in MySQL without using the ID field. I tried this, but I suppose that it doesn't work since it's based on SQL Server: how to show only even or odd rows in sql server 2008?
我试图在不使用 ID 字段的情况下从 MySQL 的表中选择所有偶数或奇数行。我试过了，但我认为它不起作用，因为它基于 SQL Server： 如何在 sql server 2008 中仅显示偶数或奇数行？
Thank you all in advance.
谢谢大家。
回答by Gordon Linoff
Assuming you have a column that specifies the ordering of the table, then you can use variables to do what you want:
假设您有一列指定表的顺序，那么您可以使用变量来执行您想要的操作：
select t.*
from (select t.*, (@rn := @rn + 1) as seqnum
from table t cross join
(select @rn := 0) vars
order by col
) t
where mod(seqnum, 2) = 0;
回答by Ankit Bajpai
Try to use this:-
尝试使用这个：-
SELECT cols
FROM (
SELECT cols, @rowNumber := @rowNumber+ 1 rn
FROM YourTable
JOIN (SELECT @rowNumber:= 0) r
) t
WHERE rn % 2 = 1;
