sql

Question 1

format of inner join

Answer 1

SELECT column1, column2 FROM “table1”
INNER JOIN “table2”
ON “table1”.”column” = “table2”.”column”
WHERE condition
GROUP BY column
ORDER BY column ASC/DESC;

Question 2

sql vs nosql database

Answer 2

• sql req FIXED predefined schema whras nosql DH predefined schema (more dynamic)
• in sql, data stored in tables w FIXED data type for each field whras for nosql, data is stored as collections of documents with NO fixed data type (X enforce constraints on data types)
• sql is ACID, nosql is flexible

Question 3

when to choose sql

Answer 3

if ACID (atomicity, consistency, isolation, durability) compliance impt + flexibility X crucial factor

Question 4

when to choose nosql

Answer 4

if flexibility impt (in adding/rmving data, when requirements of apps change over t)
+ horizontal scalibility (adding more comp) is a criteria (whr addition of low cost servers desired compared to replacing existing server w btr one) (or startups fast growing, need database to scale as they grow)

Question 5

challenges when using NoSQL

Answer 5

NoSQL X enforce constraints :. more code validation needs to be implemented

higher chance of code duplication / harder to normalise data using NoSQL bc collections cannot be joined using a query :. need be more careful to avoid breaking data integrity