SQL_notes

##pdAdmin is the GUI fo managind databases. It runs in a browser. 


##Select Statements:

SELECT * FROM public.customers -> This selects all from customers

SELECT column_name FROM public.customers -> This selects just the column name and displays it 
SELECT column_name, column_name_2 FROM public.customer -> This will return both columns. 
SELECT name, age 
SELECT public.customers.id, name, age 

## Where Clause (Conditionals)

WHERE id = 2 -> This will retung the ID position 2

WHERE id != 3 -> This will return everything BUT where id equals 3

WHERE id > 3 -> Will return all id's above 3

WHERE name = 'John' -> This will return where its exaclty John. It's not the best way to look for chars, as there might be multiple Johns. See Wildcards. 


## Wildcards (%)

WHERE name LIKE "John%" -> This means it will reaturn anything that starts with John

WHERE name LIKE "%Smith" -> This means it will return anything that ends with Simith

WHERE name LIKE "%hn%" -> This will mean anythin that has hn

WHERE name LIKE "%@%" -> This will return anything with an a @ in-between.

## AND or NOT  

WHERE email LIKE "%Smith%" AND id = 4 

WHERE email LIKE "%Smith%" OR id = 4 

WHERE NOT email LIKE "%Smith%" -> This will return everything that doesn't have Smith. 

## Order By

ORDER BY name ASC -> This will order the data ascending 

ORDER BY name DESC -> This will order the data descending. 

ORDER BY id ASC

ORDER BY column_name ASC


## Insert Into (To add to the DB)

INSERT INTO public."table_name_here"("name", "email")
VALUES ('Luis', 'luis@gmail.com')

## Update data

UPDATE public.customers
SET name = "New Updated name"
WHERE id = 6 -> This line is very important. If it's not there, it will update the entire DB

## Delete data

DELETE FROM public.customers 
WHERE id = 6

## Limit

SELECT * FROM public.customers 
LIMIT 2 -> This will limit the entire DB and just show the fist two items

LIMIT 2 OFFSET 3 -> This will limit 2 and will skip the first 3

## Inner join:
SELECT name, age -> this seelects what you want to see in your merge report 
FROM public.main_db -> This is the main table 
INNER JOIN public.secondary_db ON public.secondary_db.customer_id = public.main_db.customer.id -> This will merge the secondary DB into the main one useind the foreging key (coomin key), in this case bieng customers.id