SQL

Question 1

What is SQL and how is it different from languages like JavaScript?

Answer 1

SQL is declarative - programmer describes results they want and the computer figures it out

JavaScript is imperative - programmer writes the machine instructions

Question 2

How do you retrieve specific columns from a database table?

Answer 2

Select “column”,
“column”
From “row”;

Question 3

How do you filter rows based on some specific criteria?

Answer 3

where “column“ = ‘text value’

Question 4

What are the benefits of formatting your SQL?

Answer 4

To lessen complexity

Question 5

What are four comparison operators that can be used in a where clause?

Answer 5

Less than, greater than, equal, not equal

Question 6

How do you limit the number of rows returned in a result set?

Answer 6

limit #

Question 7

How do you retrieve all columns from a database table?

Answer 7

universal *

Question 8

How do you control the sort order of a result set?

Answer 8

Order by “column” (desc) or (asc)

Question 9

How do you add a row to a SQL table?

Answer 9

insert into “table” (“column”, “column”)
values (‘value’, value’);

Question 10

What is a tuple?

Answer 10

a list of values in SQL

Question 11

How do you add multiple rows to a SQL table at once?

Answer 11

comma separated list of tuples.

Question 12

How do you get back the row being inserted into a table without a separate select statement?

Answer 12

returning * or comma-separated column names;

Question 13

How do you update rows in a database table?

Answer 13

update “table”
set “column” = value
where “target” = target value;

Question 14

Why is it important to include a where clause in your update statements?

Answer 14

to target a specific row, others all rows would be updated.

Question 15

How do you delete rows from a database table?

Answer 15

delete
from “table”
where “target” = “target value”

Question 16

How do you accidentally delete all rows from a table?

Answer 16

by leaving out the “where” clause.

Question 17

What is a foreign key?

Answer 17

a value in one table that’s the same as value of another table to link them.

Question 18

How do you join two SQL tables?

Answer 18

from “table” join “table” using (“foreign key”)

Question 19

How do you temporarily rename columns or tables in a SQL statement?

Answer 19

select “table”.”column” as “alias”

Question 20

What are some examples of aggregate functions?

Answer 20

max(), avg (), count(), min(), sum(), every()

Question 21

What is the purpose of a group by clause?

Answer 21

to separate rows into groups and perform aggregate functions on just those groups of rows, rather than every row in table.