Failed to convert varchar value to data type int

This is the error that may occur in the stored procedure.

Like what

Use [School]
go
alter Procedure [dbo].[ S_get_student]
(
	@sex int	--gender sex:1 (male) 2 (female)
)
as
begin
	declare @sql varchar (max)-- Can contain many many characters
	set @sql = ' SELECT * FROM dbo. Class where sex ' + @sex
	exec (@sql)
end

--[s_get_student] 1

This situation prompts

Message 245, Level 16, State 1, Process s_get_student, line 8th
In the varchar value ' SELECT * FROM dbo. Class where sex ' conversion to data type int failed.
This is because your @sql is varchar value, and your @sex is shaping data

So you're going to convert @sex to the data type, and replace it with varchar.

Set @sql = ' SELECT * FROM dbo. Class where sex= ' +convert (varchar, @sex)

And, of course, it doesn't rule out anything else. You make the type of the concatenation statement the same for your variable convert (varchar,@x) because you can't add a date or an integer to a string

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