sql server - insert unique values only -

i need find efficient way insert value table when value not in table.

here sample table:

declare @table table (thevalue int primary key) 

sample data insert:

insert @table select 1 union select 2 union select 3 --existing data declare @x int;set @x=5                              --data add 

here ideas can think of this. 1 best and/or there better way? batch process, there no risk of process inserting data, no locking necessary in try 1.

try 1:

if not exists (select 1 @table thevalue=@x) begin     insert @table values (@x) end 

try 2:

insert @table select @x except select thevalue @table 

try 3:

insert @table select @x @x not in (select thevalue @table) 

try 4:

begin try     insert @table values (@x) end try begin catch end catch 

here's 1 other way self joining table inserting , inserting records doesn't exist.

first table doing batch inserts to, want maintain unique records. keep in mind should have unique constraint on here. want use 1 of these unique inserts never run constraint:

declare @table table (thevalue int primary key)  

one of tables getting data want insert main batch table:

declare @tableselectingfrom table (thevalue int primary key)  

for example, populating record:

insert @tableselectingfrom select 1 

there's left outer join pull unique records @tableselectingfrom:

insert @table  select a.thevalue @tableselectingfrom left join @table b on a.thevalue = b.thevalue b.thevalue null  select * @table