Sql 使用union将数据类型varchar转换为bigint时出错

查询：

错误：

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将数据类型varchar转换为bigint时出错。

在

联合之后，列的顺序错误。以下是更正版本：

SELECT TOP (1) '-1' AS hrempid, 'All employees' AS fullname
FROM employee
UNION
SELECT fullname, hrempid
FROM employee AS employee1 
order by fullname

更妙的是，使用类似这样的方法：

SELECT   TOP (1) '-1' AS hrempid, 'All employees' AS fullname
FROM     employee
UNION
SELECT   hrempid, fullname
FROM     employee AS employee1 
ORDER BY fullname

在
hrempid
周围保留
”
，然后切换列。试试这个：

SELECT   CAST(-1 AS BIGINT) AS hrempid, 'All employees' AS fullname
UNION ALL
SELECT   hrempid, fullname
FROM     employee AS employee1 
ORDER BY fullname

SELECT TOP (1) 'All employees' AS fullname, -1 AS hrempid
FROM employee
UNION
SELECT fullname, hrempid
FROM employee AS employee1 
order by fullname