1. Prepared Statements Function and Triggers
SQL prepared statement
SQL Functions
SQL Triggers

2. SQL prepared statements
Create prepared statement and execute it:
DELIMITER //
create procedure p30(search_value int)
begin
= concat('select * from t where s1 = ', search_value);
prepare st
execute st;
end; //
//DELIMITER ;

3. SQL prepared statements
Exercise:
Create a prepared statement that will search and return the row with employee ID number 8?

4. SQL Functions What is the different between procedure and functions?
Functions look a lot like procedures. The only noticeable syntax differences are that we say create function instead of create procedure, and we need a RETURNS clause to say what the data type of the function is, and we need a RETURN statement because a function must return a value.

5. SQL Functions Functions are declared using the following syntax:
function <function-name> (param_spec1, …, param_speck)
returns <return_type>
[not] deterministic allow optimization if same output
for the same input (use RAND not deterministic )
Begin
-- execution code
end;
where param_spec is:
[in | out | in out] <param_name> <param_type>
You need ADMIN privilege to create functions on mysql-user server

6. SQL Functions CREATE FUNCTION DELIMITER //
CREATE FUNCTION giveRaise (oldVal double, amount double)
Return double
Deterministic
BEGIN
declare newVal double;
set newVal = oldVal * (1 + amount);
return newVal;
END; //
DElMITER ;
Now lets use the function that we have created
SELECT emp_name, salary, giveRaise(salary, 0.1) as newSalary
FROM employee;

7. SQL Triggers
To monitor a database and take a corrective action when a condition occurs
Examples:
Charge $10 overdraft fee if the balance of an account after a withdrawal transaction is less than $500
Limit the salary increase of an employee to no more than 5% raise
CREATE TRIGGER trigger-name trigger-time trigger-event ON table-name FOR EACH ROW trigger-action;
trigger-time  {BEFORE, AFTER}
trigger-event  {INSERT,DELETE,UPDATE}

8. Triggers Example Triggers Example:
We want to create a trigger to update the total salary of a department when a new employee is hired
delimiter //
create trigger update_salary
after insert on employee
for each row
begin
if new.dept_no is not null then
update deptsal
set totalsalary = totalsalary + new.salary
where dept_no = new.dept_no;
end if;
end ; //
delimiter ;
The keyword new refers to the new row inserted

9. Triggers Example continued
First lets update the deptsal table and set the totalsalry to 0
update deptsal set totalsalary = 0;
Call the updateSalary procedure to calculate the totalsalary of all rows
call updateSalary();
Lets verify the totalsalary of each department in detpsal table the insert the following rows
insert into employee values (9, 'Fred', null, 1, );
Now it time to verify if the trigger works
Select * from deptsal;
Try to insert an other row and see what happens?

10. Triggers continued Exercise:
Create a trigger to update the total salary of a department when an employee row is modified.
Try modify a row in the employee table and verify the changes in totalsalary.
Create a trigger to update the total salary of a department when an employee tuple is deleted
Try to modify a row in the employee table and verify the changes in totalsalary.