使用 union 将数据类型 varchar 转换为 bigint 时出错

【问题标题】：Error converting data type varchar to bigint using union使用 union 将数据类型 varchar 转换为 bigint 时出错
【发布时间】：2012-03-16 03:14:09
【问题描述】：

查询：

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

错误：将数据类型 varchar 转换为 bigint 时出错。

【问题讨论】：

标签： sql

【解决方案1】：

union 之后的列顺序错误。这是修正版：

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

更好的是，使用这样的东西：

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

【讨论】：

【解决方案2】：

将' 留在您的hrempid 周围并切换列。试试这个：

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

【讨论】：