SQL Subquery issue 3 - mysql

Question

I have a issue with my SQL code.
When I run this code I'm getting such error mesage:
**
Subquery returned more than 1 value. This is not permitted when the
subquery follows =, !=, <, <= , >, >= or when the subquery is used as
an expression.
**
I don't know how to correct this code to run it?
Can somebothy look at it and help me with it?
Thank you for your help,
SELECT dbo.FRA$.[GUID], dbo.FRA$.[Last Name],
dbo.FRA$.[First Name], dbo.FRA$.[HR Manager Last Name],
dbo.FRA$.[HR Manager First Name], (SELECT dbo.FRA$.[Business Email Address] FROM dbo.FRA$ t WHERE t.[HR Manager ID] = t.[Emplid]) AS [HR Manager E-Mail],
dbo.LOC.Descr AS [COMPANY NAME], dbo.FRA$.[Location Code],
dbo.LOC.[ADDRESS], dbo.LOC.Postal, dbo.LOC.City, dbo.FRA$.[National ID], dbo.FRA$.[Current Employee Class Desc] AS [Current Empl Class],
dbo.FRA$.[Contract type description] AS [CONTRACT TYPE], dbo.FRA$.[Business Title],
CASE dbo.FRA$.[Current Employee Class Desc]
WHEN 'Operator' THEN 10
WHEN 'Clerical worker' THEN 22
WHEN 'Technician' THEN 32
WHEN 'Supervisor' THEN 33
WHEN 'Manager&Engineer' THEN 54
END AS [Salary brutto],
FORMAT(dbo.FRA$.[Birthdate],'yyyy-MM-dd') AS [Birth Date], FORMAT(dbo.FRA$.[Last Start Date],'yyyy-MM-dd') AS [Hire Date]
FROM dbo.FRA$
INNER JOIN dbo.LOC
ON dbo.FRA$.[Location Code] = dbo.LOC.[Location]
WHERE [HR Status] IN ('International Assignment','Active','Leave of Absence');

Answer 1

Try to replace
SELECT dbo.FRA$.[Business Email Address] FROM dbo.FRA$ t WHERE t.[HR Manager ID] = t.[Emplid]
with
SELECT TOP 1 t.[Business Email Address] FROM dbo.FRA$ t WHERE [HR Manager ID] = t.[Emplid]
it will take only one row from rows returned by your subquery