Marking users as not active if they don't have required records

I have a simple table model. There are some required "Actions" that every user has to have completed.

User
-Id

-Name
-IsActive

Actions
-Id
-Name

UserActions
-UserID
-ActionID

I want to find all Users who don't have all the Action records in the UserAcitons table. If they don't have all actions records in UserActions, I want to mark IsActive as false.

There could be 20K users so this should be effecient to process.

Looking for the best way to do this without having a cursor.

Assuming rows in UserActions are unique, you can count the actions in the two tables and compare them:

update u
    set isactive = (case when num_actions > total_actions then 1 else 0 end)
    from users u left join
         (select ua.userid, count(*) as num_actions
          from useractions ua
          group by ua.userid
         ) ua
         on ua.userid = u.id cross join
         (select count(*) as total_actions
          from actions a
         ) a;

SQL Server doesn't support booleans, so this uses 0 for false and 1 for true.

You forgot to tell us some details, for example if there are duplicated actions, if ids are UNIQUE, etc.
for very simple scenario I managed to create the below example:

create table [User]
(
 Id int not null primary key,
 Name varchar(50) not null,
 IsActive bit not null
)

create table [Actions]
(
 Id int not null primary key,
 Name varchar(50) not null
)
GO

create table [UserActions]
(
 UserId int not null,
 ActionId int not null,
 foreign key (UserId) REFERENCES [User](Id),
 foreign key (ActionId) REFERENCES [Actions](Id)
)
GO
insert into [User] values
(1, 'Alice', 1),(2, 'Bob', 1),(3, 'Caroline', 1)

insert into [Actions] values
(1, 'eat'),(2,'drink'),(3,'sleep')

insert into [UserActions] values
(1,1),(1,2),(1,3),
(2,1),(2,2),
(3,1),(3,2),(3,1)
GO


update us
set us.IsActive = 0
from [User] us
join 
(
	select ua.UserId, COUNT(distinct ua.ActionId) as ActionCount
	from [UserActions] ua
	group by ua.UserId
) as uac on uac.UserId = us.Id
where uac.ActionCount < (select count(*) from [Actions])

select * from [User] us

Provides de results below

> Id Name IsActive
> ----------- ---------- --------
> 1 Alice 1
> 2 Bob 0
> 3 Caroline 0