java - MYSQL 中特定列中的重复项显示为空

Question

我在 MySQL 中有一个名为 Bills 的表。

Bill         item          totalprice

BILL_1       Fossil Watch  9000
BILL_1       Fastrack      9000
BILL_1       Fastrack      9000
BILL_2       Woodlands     7000
BILL_2       Woodlands     7000
BILL_3       Denim Shirt   9000
BILL_3       Levis Jean    9000

SELECT 语句应返回如下所示

Bill         item          totalprice

BILL_1       Fossil Watch  9000
BILL_1       Fastrack      -
BILL_1       Fastrack      -
BILL_2       Woodlands     7000
BILL_2       Woodlands     -
BILL_3       Denim Shirt   9000
BILL_3       Levis Jean    -
The totalprice column is total bill amount.

Answer 1

不确定这是否是您真正想要的，但尝试一下:

select t.Bill, t.item, t.totalPrice
from (
    select 
        b.Bill, b.item
        ,if(@price <> b.totalPrice or @price is null, b.totalPrice, '-') as totalPrice
        ,@price := b.totalPrice as dummy
    from (select * from Bills order by totalPrice desc, item desc) b
    cross join (select @price := null) t
) t

Demo Here

已编辑:

select t.Bill, t.item, t.totalPrice
from (
    select 
        b.Bill, b.item
        ,if(@price <> b.totalPrice or @price is null, b.totalPrice, '-') as totalPrice
        ,@price := b.totalPrice as dummy
    from (select * from Bills order by Bill, totalPrice desc) b
    cross join (select @price := null) t
) t

New Demo