MySQL how to use check? - mysql

Question

I am a very beginner in MYSQL and I am trying to use CHECK for EmployeeID is in the format of E### where "#" is the number(int). ANd the DOB that is eneterd should be 16 years or older from current date. Here is the code for the table. Thanks for help!
Create table Employee(
EmployeeID varchar(200) not null primary key,
DOB date,
##Check (DOB <= CURRENT_DATE - interval '16' year),
FirstName varchar(200),
MiddleName varchar(200),
LastName varchar(200),
Address varchar(255),
StartDate date,
Gender varchar(100)
);

Answer 1

I would use a regular expression to confirm the validity of the EmployeeID, such as this :-
EmployeeID varchar(200) not null primary key CHECK EmployeeID REGEXP 'E\d{3}',

Answer 2

Other answers covered using the check constraints.
However, if it's always going to start with an 'E', do you need to store the 'E'? Can you store just the integer and add the E later? An integer primary key is simpler, faster, smaller, and more robust.
Use a generated column to provide the ID with the E on it.
create table Employee (
-- No check required, it's an integer by definition.
-- Takes less storage to store and index.
ID integer primary key,
-- A generated virtual column (takes no storage space)
EmployeeID varchar(255) as (concat('E', id)) virtual
);
insert into Employee (id) values (1), (23), (456);
select * from Employee;
ID EmployeeID
1 E1
23 E23
456 E456
select * from Employee where EmployeeID = 'E456';
ID EmployeeID
456 E456
Try it.