Question

我要通过升序数值来订购sql结果。我的代码是这样的：

ORDER BY CAST(`baseData` AS DECIMAL(10,2)) {$dir} ";

它工作得很好，但是有一个问题：它将所有NULL值放在底部，我认为它们认为它们像“0”。我需要在底部放置所有NULL值，我该如何修改它？

Answer 1

试试这个SQL

对于MYSQL

ORDER BY COALESCE(CAST(`baseData` AS DECIMAL(10,2)),0)

对于Oracle

ORDER BY NVL(CAST(baseData AS DECIMAL(10,2)),0)

SQL Fiddle

MySQL 5.5.30架构设置：

create table test(
t varchar(5)
);


insert into  test
values('123'),('234'),('222'),(NULL);

查询1 ：

select coalesce(cast(t as decimal(10,2)),0)
from test
order by coalesce(cast(t as decimal(10,2)),0);

<强> Results ：

| COALESCE(CAST(T AS DECIMAL(10,2)),0) |
----------------------------------------
|                                    0 |
|                                  123 |
|                                  222 |
|                                  234 |

Answer 2

如果你想把所有Null放在头上

  ORDER BY CAST(`baseData` AS DECIMAL(10,2)) NULLS FIRST

如果你想把所有Null放在底部

  ORDER BY CAST(`baseData` AS DECIMAL(10,2)) NULLS LAST

如果您希望将Null视为0，则将它们转换为Pheonix

  ORDER BY Nvl(CAST(`baseData` AS DECIMAL(10,2)), 0) -- Oracle, MS SQL
  ORDER BY IfNull(CAST(`baseData` AS DECIMAL(10,2)), 0) -- MySQL

如果你想让Null成为最后一个，但显示为0

  select ...
         Nvl(CAST(`baseData` AS DECIMAL(10,2)), 0) -- Oracle, MS SQL
         ...
   order by CAST(`baseData` AS DECIMAL(10,2)) NULLS LAST

Answer 3

是的，它有效：

ORDER BY baseData = '', CAST(`baseData` AS DECIMAL(10,2)) {$dir} ";

SQL具有NULL值时的排序

3 个答案: