Question

我有这个表，我想把它分成三个表，所以我有名字，名称和订单之间的关系表，第三个只包含订单。所以我认为一个简单的方法是在这里添加一个唯一的数字列

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我想添加一个数字列，其中包含与唯一+----+------+-----------------------+-------+--------------+ | id | name | address | phone | order_number | +----+------+-----------------------+-------+--------------+ | 1 | Joe | Joes Address | 1111 | 1390842 | | 2 | Paul | Pauls Address | 2222 | 9082309 | | 3 | Greg | Gregs Address | 3333 | 0928340 | | 4 | Lucy | Lucys Address | 4444 | 9028340 | | 5 | Paul | Pauls Address | 2222 | 8958399 | | 6 | Tom | Toms Address | 5555 | 9084024 | | 7 | Lucy | Lucys Another Address | 4444 | 9801983 | | 8 | Paul | Pauls Another Address | 2222 | 0982304 | +----+------+-----------------------+-------+--------------+值相关联的增量编号，以便预期结果为

name

我该怎么办？

Answer 1

使用用户定义的变量

与您想要的结果集相似的一些内容

public void method() {
    // declare variables...

    if (Character.toUpperCase(choosePassOverPed) == 'Y') {
        passengerPoints = passengerPoints + toughCallThresholdPoints;
        checkPoints(passengerPoints, pedestrianPoints, numAdultPedestrians, numChildPedestrians, numAdultPassengers, numChildPassengers);
    } else {
        pedestrianPoints = pedestrianPoints + toughCallThresholdPoints;
        checkPoints(passengerPoints, pedestrianPoints, numAdultPedestrians, numChildPedestrians, numAdultPassengers, numChildPassengers);
    }
}

private static void checkPoints(int passengerPoints, int pedestrianPoints, int numAdultPedestrians, int numChildPedestrians, int numAdultPassengers, int numChildPassengers) {
    if (passengerPoints > pedestrianPoints) {
        System.out.println("Fatality Group: PEDESTRIANS");
        log(numAdultPedestrians, numChildPedestrians);
    } else {
        System.out.println("Fatality Group: OCCUPANTS");
        log(numAdultPassengers, numChildPassengers);
    }
}

private static void log(int numAdultPedestrians, int numChildPedestrians) {
    System.out.printf("Number of adult fatalities: %d%n", numAdultPedestrians);
    System.out.printf("Number of child fatalities: %d%n", numChildPedestrians);
}

DEMO

另一个简单版本，假设id列设置为自动递增，如果是，那么您可以使用相关子查询来选择相同名称记录的最小ID

select `id`, `name`, `address`, `phone`, `order_number`,
@b:= case when `name` <> @a then @b + 1 else @b end NID,
@a:= `name`
from (
    select *
    from demo b,
    (select @a:=null,@b:=1) a
    order by name 
) c

上面的注释不保证它完全依赖于id列值的序列

DEMO

Answer 2

如果您只是想显示NID，那么@M Khalid Junaid的答案将会正常运作。

但是如果你想在表格中添加列NID，那么以下查询将完成工作：

alter table t
add column nid integer;

update t
set nid = (Select 
           (case when count(name)>1 then min(id)
                 else  id
            end)
           from
           (select *from t) x
           where t.name = x.name          
           );

注意：Nid不包含增量序列。它基于id列。

希望它有所帮助！

MYSQL：根据唯一行值向表中添加唯一数值？

2 个答案: