SQL Flashcards
(27 cards)
What is PostgreSQL and what are some alternative relational databases?
it’s an open source relational database, alts are mySQL, SQLite, SnowFlake
What are some advantages of learning a relational database?
they’re everywhere so if you learn one, you learn a lot of them
What is one way to see if PostgreSQL is running?
check top or sudo service postgresql status
What is a database schema?
a collection of tables in a database
What is a table?
a list of rows all having the same attributes
What is a row?
one entry in a table that has an attribute value
What is SQL and how is it different from languages like JavaScript?
its a declarative language vs JS is imperative
How do you retrieve specific columns from a database table?
select “column name”
“additional columns. . .”
from “table name”;
How do you filter rows based on some specific criteria?
where clause and an expression that evaluates to a boolean
What are the benefits of formatting your SQL?
readability
What are four comparison operators that can be used in a where clause?
=, >, < !=
How do you limit the number of rows returned in a result set?
limit clause
How do you retrieve all columns from a database table?
select *
How do you control the sort order of a result set?
order by clause with asc and desc
How do you add a row to a SQL table?
insert into statement
What is a tuple?
a list of values that may or may not correspond to a row in a table
How do you add multiple rows to a SQL table at once?
insert into with one list of columns followed with multiple tuples
How do you get back the row being inserted into a table without a separate select statement?
returning *
How do you update rows in a database table?
update keyword(update “tableName” set “column” = ‘value’)
Why is it important to include a where clause in your update statements?
if you don’t it will update every row
How do you delete rows from a database table?
delete keyword (delete from “table” where “something” = something else)
How do you accidentally delete all rows from a table?
by not including a where clause
What is a foreign key?
rows between tables with shared values
How do you join two SQL tables?
join “table” using (“key”)
