select DATEDIFF( day,'2021-12-01' , '2021-12-31' ) + 1 - ( 2 * DATEDIFF( week , '2021-12-01' , '2021-12-31' ) + Case When DATEPART( dw , '2021-12-01' ) = 1 Then 1 Else 0 End + Case When DATEPART( dw , '2021-12-31' ) = 7 Then 1 Else 0 End ) as 工作天数 

select count(1) ct

from master.dbo.spt_values 

where type='P' and

number<=datediff(d,stuff(convert(varchar,getdate(),23),9,2,'01'),DATEADD(m, DATEDIFF(m,0,getdate())+1, 0))

and datepart(dw,dateadd(d,number,stuff(convert(varchar,getdate(),23),9,2,'01')))

not in(1,7)

参考下

https://www.pianshen.com/article/85891115015/

select * from (

select convert(char(7),getdate(),120)+'-'+right('0'+convert(varchar(2),number),2) as [日期格式1] 

,DATEPART(W,convert(char(7),getdate(),120)+'-'+right('0'+convert(varchar(2),number),2)) as [week]

from master..spt_values with(nolock) 

where type='P' and number>=1 

--and number<=datediff(dd,getdate(),dateadd(mm,1,getdate())) --对于mssql而言该语句不试用于2013-08-31的情况，这时由于9月没有31号，固计算出来的天数是30天 

and number<=datediff(dd,convert(char(7),getdate(),120)+'-01',convert(char(7),dateadd(mm,1,getdate()),120)+'-01')--转换为1号来计算天数

) a where week not in ('6','7')

PS:默认星期日是一周开始，若需要改语句前加

set datefirst 1---设置SQL一周从周一开始

set datefirst 7---设置SQL一周从周日开始

select 

count(t.dateaaa)-sum(t.xqj) as ts

 from (

SELECT

case when datepart(dw,  

CONVERT(VARCHAR(10),DATEADD(DAY,number,LEFT('2021-12-01',8) + '01'),120))>5 then 1 else 0 end as xqj,

CONVERT(VARCHAR(10),DATEADD(DAY,number,LEFT('2021-12-01',8) + '01'),120) as dateaaa

FROM master..spt_values

WHERE type = 'P' 

AND (number BETWEEN 0 AND 32) 

AND DATEADD(DAY,number,LEFT('2021-12-01',8) + '01') 

< DATEADD(MONTH,1,LEFT('2021-12-01',8) + '01')

) t 

where 1=1