如何从 table 分配日期变量值？

Question

以下代码：

declare @tradeDate date = select tradeDate from tSystemStatus

产生错误：

Incorrect syntax near the keyword 'select'.

table结构：

CREATE TABLE [dbo].[tSystemStatus](
    ....
    [TradeDate] [date] NOT NULL,
    ....

我做错了什么？

Answer 1

试试这个

declare @tradeDate date = (select tradeDate from tSystemStatus)

但是如果select查询return多于一个值，那么它会抛出错误（你可以在这里使用top 1）

declare @tradeDate date = (select top 1 tradeDate from tSystemStatus)

或者

declare @tradeDate date 
select @tradeDate = tradeDate from tSystemStatus

Answer 2

试试这个

declare @tradeDate date;
select @tradeDate=tradeDate from tSystemStatus

How to assign date variable value from table?