sql server 奇葩问题

SELECT DISTINCT
	a.*
FROM
	employeeInfo a
LEFT JOIN (
	SELECT
		b.buiness
	FROM
		quaData b,
		qualificationsInfo c
	WHERE
		b.qualificationsInfoId = c.qualificationsInfoId
	AND c.qfType = 1
	AND c.state = 1
	AND b.state = 1
) dd ON a.employeeInfoId = dd.buiness

SELECT
	a.*
FROM
	employeeInfo a
LEFT JOIN (
	SELECT
		b.buiness
	FROM
		quaData b,
		qualificationsInfo c
	WHERE
		b.qualificationsInfoId = c.qualificationsInfoId
	AND c.qfType = 1
	AND c.state = 1
	AND b.state = 1
) dd ON CONVERT (
	VARCHAR (100),
	a.employeeInfoId
) = dd.buiness

其中quaData中的buiness字段是varchar类型的，存的值是英文和数字。

第一段代码去掉distinct就不行了，会报错：[Err] 22018 - [SQL Server]在将 varchar 值 'e10c9cb3d30b4b4cb1721561a31db513' 转换成数据类型 int 时失败。

不用distinc却确实t会有重复的结果