SQL将nchar与字符串进行比较

Question

我有两列：

• id（nchar）
• name（varchar）

简单的事情无法弄清楚如何。

    select *
    from plant.carrier
    where carrier_id like 'NT'

这会产生表达式错误

      SELECT *
      FROM plant.carrier
      WHERE RTrim(CAST([carrier_id] As VarChar) = 'NT'

id列

CREATE TABLE [plant].[carrier](
    [carrier_id] [nchar](4) NOT NULL,
    [name] [nvarchar](30) NOT NULL,
 CONSTRAINT [PK_carrier] PRIMARY KEY CLUSTERED 
(
    [carrier_id] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS =enter code here ON, ALLOW_PAGE_LOCKS = ON, FILLFACTOR = 90) ON [PRIMARY]
) ON [PRIMARY]
GO

Answer 1

要比较nchar和varchar，您需要将char转换为varchar并比较两个varchars：

RTrim(CAST([nCharColumn] As VarChar)

<强>更新

以下是完整示例：

create table test (
f nchar(20))

insert into test values('nt')
insert into test values('st')

declare @s varchar(20) = 'nt'
select * from test where rtrim(cast(f as varchar)) = @s

更新2

CREATE TABLE [carrier](
    [carrier_id] [nchar](4) NOT NULL,
    [name] [nvarchar](30) NOT NULL,
 CONSTRAINT [PK_carrier] PRIMARY KEY CLUSTERED 
(
    [carrier_id] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF,  ALLOW_PAGE_LOCKS = ON, FILLFACTOR = 90) ON [PRIMARY]
) ON [PRIMARY]

GO

insert into carrier values('nt', 'nt')
insert into carrier values('st', 'st')

declare @s varchar(20) = 'nt'
select * from carrier where rtrim(cast([carrier_id] as varchar)) = @s

这也适合我。它返回一条记录。

Answer 2

如果您Read The Documentation，您会发现[var]char和n[var]char之间的转换是隐含的，所以请说

where x.some_char_column = y.some_nchar_column

应该工作得很好......除非列定义的排序规则不同。那你可能有问题。

Answer 3

在比较字符串值时不要使用rtrim。无论数据类型是（n）char还是（n）varchar，sql server都会忽略任何字符串右侧的空格以进行相等性检查。

对原件的这些轻微修改都应该可以正常工作。它们都与您发布的表格一起使用。

select *
from carrier
where carrier_id like 'NT%'

SELECT *
FROM carrier
WHERE [carrier_id] = 'NT'