sp_addrolemember (Transact-SQL MetaData) Definition

Please note: that the following source code is provided and copyrighted by Microsoft and is for educational purpose only.
The meta data is from an SQL 2012 Server.

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Definition:

sys.sp_addrolemember(nvarchar @rolename
, nvarchar @membername)

MetaData:

 --  FOR BACKWARD COMPATIBILTY ONLY --   
create procedure sys.sp_addrolemember  
    @rolename       sysname,  
    @membername     sysname  
AS  
    --  SETUP RUNTIME OPTIONS / DECLARE VARIABLES --   
    set nocount on  
    declare @ret        int,    --  return value of sp call  
            @memuid     int,  
            @stmtR        nvarchar(4000)  
  
    --  Was a part of check to prevent inside a user Xact. Leave for backward compat.--   
    set implicit_transactions off  
  
    exec @ret = sys.sp_validname @rolename  
    if @ret <> 0  
        return(1)  
  
    exec @ret = sys.sp_validname @membername  
    if @ret <> 0  
        return(1)  
  
    BEGIN TRANSACTION  
  
        --  EXCL LOCK MEMBER --   
        EXEC %%Owner(Name = @membername).Lock(Exclusive = 1) --  may fail  
  
        --  ATTEMPT ADDING IMPLICIT ROW FOR NT NAME --   
        if @@error <> 0    --  not found  
        begin  
            EXEC @ret = sys.sp_MSadduser_implicit_ntlogin @membername  
            if (@ret <> 0)  
            begin  
                ROLLBACK TRANSACTION  
                raiserror(15410, -1, -1, @membername)  
                return (1)  
            end  
            --  Member locked by sp_MSadduser_implicit_ntlogin  
        end  
  
        set @stmtR = 'alter role '  
        set @stmtR = @stmtR + quotename(@rolename, ']')  
        set @stmtR = @stmtR + ' add member '  
        set @stmtR = @stmtR + quotename(@membername, ']')  
  
        --  issue DDL to create the role --   
        exec (@stmtR)      
        if @@error <> 0  
        begin  
            ROLLBACK TRANSACTION  
            return (1)  
        end  
  
    --  RETURN SUCCESS --   
    COMMIT TRANSACTION  
    return (0) --  sp_addrolemember