Creating triggers and Stored proceedures

Question

. Can someone pls give me codes to execute following things?
*create sql server triggers to prevent deletion of primary key in employee table (primary key is emp_id)
 *create stored procedures,
1.to obtain employee details, company he's working in and the manager's name, any changes to the database 
2.update if something is successful in operations
These are all the codes in my query for you to understand my requirement
create table employee
(emp_id nvarchar(20) primary key,
employee_name varchar(20),
street varchar(20),
city varchar(20))
create table company
(company_name varchar(20) primary key,
city varchar(20))
create table works
(emp_id nvarchar(20),
company_name varchar(20),
salary int,
HireDate date)
create table manages
(emp_id nvarchar(20),
manager_name varchar(20))
Insert into employee values('101','Scott Matthews','Netson street','Auckland')
Insert into employee values('102','Jonah Black','Wills street','Wellington')
Insert into employee values('103','Karen Ole','Manners street','Wellington')
Insert into employee values('104','Ben Dawson','Queen Street','Wellington')
Insert into employee values('105','Norah Jones','Symonds street','Auckland')
Insert into company values('TSB','Wellington')
Insert into company values('ABC','Auckland')
Insert into works values('101','ABC','20000','12-09-2009')
Insert into works values('102','TSB','40000','06-10-2009')
Insert into works values('103','ABC','50000','05-09-2009')
Insert into works values('104','ABC','60000','11-09-2008')
Insert into works values('105','ABC','80000','08-09-2009')
Insert into manages values('101','Norah Jones')
Insert into manages values('102','Norah Jones')
Insert into manages values('104','Norah Jones')
Thanks!

Answer 1

Thanks! but it gives this error message
Msg 208, Level 16, State 6,
Procedure trg_AvoidPKDeletion, Line 1
Invalid object name 'trg_AvoidPKDeletion'.
Once I execute this code, I shouldn't be able to delete any emp_id from the table by going to it's edit option. that's what done by this
trigger right?
sorry it should be this
CREATE TRIGGER trg_AvoidPKDeletion
ON DATABASE
FOR ALTER_TABLE
AS
BEGIN
DECLARE @SQLCommand varchar(max)= EVENTDATA().value('(/EVENT_INSTANCE/TSQLCommand)[1]', 'nvarchar(max)')
IF EXISTS (select s.name as TABLE_SCHEMA, t.name as TABLE_NAME
, k.name as CONSTRAINT_NAME, k.type_desc as CONSTRAINT_TYPE
, c.name as COLUMN_NAME, ic.key_ordinal AS ORDINAL_POSITION
from sys.key_constraints as k
join sys.tables as t
on t.object_id = k.parent_object_id
join sys.schemas as s
on s.schema_id = t.schema_id
join sys.index_columns as ic
on ic.object_id = t.object_id
and ic.index_id = k.unique_index_id
join sys.columns as c
on c.object_id = t.object_id
and c.column_id = ic.column_id
where k.type_desc = 'PRIMARY_KEY_CONSTRAINT'
AND @SQLCommand = 'ALTER TABLE ' + s.name + ' DROP CONSTRAINT ' + k.name )
PRINT 'PK constraints cannot be dropped'
ROLLBACK
END
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