This might just help!!!!!!!!!
Use Databasename;
------------------------------------------ Alters the table you can ADD or Drop a column or Rename etc.
Rename Table employees TO workers;
Rename Table workers TO employees;
Alter Table employees
Add phone_number Varchar(15);
Alter Table employees
Rename Column phone_number To email;
Alter Table employees
Modify Column email Varchar(100);
Alter Table employees
Modify email Varchar(100)
After last_name; You could also write First
Alter Table employees
Drop Column email;
()()()()()()()()()()()()()()()()()()()() Add a column in an existing table, and insert data into that row.
Alter Table Employees
Add Column job Varchar(25);
Select * from employees;
Update employees
Set job = "Manager"
Where Employee_id = 1;
Select * from employees;
------------------------------------------ Pay attention to the datatype (for date that = year then month then day)
Insert Into employees
Values (1, "Eugene", "Krabs", 25.50, "2023-01-02");
Select * From employees;
------------------------------------------ Inserts values into an existing table.
Insert into employees
Values (2, "Squidward", "Tentacles", 15.00, "2023-01-03"),
(3, "SpongeBob", "Squarepants", 12.50, "2023-01-04"),
(4, "Patrick", "Star", 12.50, "2023-01-05"),
(5, "Sandy", "Cheeks", 17.50, "2023-01-06");
Select * From employees;
------------------------------------------ Inserts values into an existing table, but this one specifies the parts that will be added.
Insert into employees (Employee_ID, First_name, Last_name)
Values (6, "Sheldon", "Plankton");
Select * From employees;
------------------------------------------ Shows a list of table employee's first name and last name.
Select First_name, Last_name
From employees;
------------------------------------------ this shows all the values from table employees for employee_id 3.
Select *
From employees
Where emplyee_id = 3;
Select *
From employees
Where first_name = "SpongeBob";
------------------------------------------ Shows the data from table employees hourly_pay higher than 15. >=
Select *
From employees
Where hourly_pay >= 15;
> can also be used solo, meaning Greater then
>= means Greater than or equal to.
------------------------------------------ shows all data from table employees hire_date Lower than 2023-01-03. <=
Select *
From employees
Where hire_date <= "2023-01-03";
< can also be used solo, meaning Lesser than
<= means lesser than or equal to.
------------------------------------------ AND-OR-NOT-BETWEEN-IN
Select *
From employees
Where hire_date < "2023-01-05" AND job = "cook";
Select *
From employees
Where job = "cook" OR job = "cashier";
Select *
From employees
Where Not job = "manager" AND NOT job = "asst. Manager'';
Select *
From employees
Where hire_date BETWEEN "2023-01-04" AND "2023-01-07'';
Select *
From employees
Where job IN ("cook", "cashier", "janitor");
------------------------------------------ Updates the table employees the sets the pay to 10.25 for employee that has employee_id 6.
Update employees
Set hourly_pay = 10.25
Where emplyee_id = 6;
Select * From employees;
------------------------------------------ This also updates the hourly pay but also the hiring date of employee_id 6.
Update employees
Set hourly_pay = 10.50,
hire_date = "2023-01-07"
Where emplyee_id = 6;
Select * From employees;
()()())()()()())()()()))()()()()()( Updating from existing data.
Update employees
Set frst_name = "Smelldon"
Where employee_id = 6;
Select * From employees;
------------------------------------------ Sets the hire date to NULL, meaning that there is no data there.
Update employees
Set hire_date = NULL
Where employee_id = 6;
Select * From employees;
------------------------------------------ This updates the hourly pay for all the employees (Or in simpler a whole column)
Update employees
Set hourly_pay = 10.25;
Select * from employees;
------------------------------------------ This deletes from table employees, employee_id 6.
Delete From employees
Where enployee_id = 6;
Select * From employees;
------------------------------------------ WILDCARD-this will show all the first names with the letter S etc.
"S%" will show everything that begins with the letter S.
"%R" will show everything that ends with the letter R.
Select * From employees
Where first_name Like "S%";
Select * From employees
Where hire_date Like "2023%";
Select * From employees
Where last_name Like "%r";
------------------------------------------ AVERAGE - Shows an average from column hourly_pay or sum
Select AVG(hourly_pay)
from employees;
Select SUM(hourly_pay)
From employees;
