primary key and foreign key

primary should be unique and cannot be null foreign key can have duplicates and can be null

core interfaces in JDBC

driver, connection, statement, result set

difference between WHERE and HAVING clauses

-having is used when we have multi row function -where is conditions that dont have multi row function

difference between GROUP BY and ORDER BY

- GROUP BY: groups data and used with aggregate functions - ORDER BY: ordering data in ascending and descending order

difference between INNER, JOIN, LEFT JOIN, RIGHT JOIN, FULL JOIN

-INNER JOIN: returns only matching rows - LEFT JOIN: returns all rows from left table and matching rows from right - RIGHT JOIN: returns all rows from the right table and matching in left - FULL JOIN: returns all rows from both sides

query to get 2nd largest salary from employees table

select Max(salary) as second_highest_salary from employees where salary<select (max(salary) from employees)

difference between DELETE, TRUNCATE and DROP

-DELETE: deletes specific data from table - TRUNCATE: deletes all data from table - DROP: deletes data and table structure

counts grouped by a column

using count() aggregate and group by clause

validate api responses against database values

inspect http status code, check response headers and content, verify data accuracy

write sql queries in automation framework

using prepared statement and statement

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SQL questions

Question	Answer
primary key and foreign key	primary should be unique and cannot be null foreign key can have duplicates and can be null
core interfaces in JDBC	driver, connection, statement, result set
retrieve unique records from table	using select distinct
difference between WHERE and HAVING clauses	-having is used when we have multi row function -where is conditions that dont have multi row function
difference between GROUP BY and ORDER BY	- GROUP BY: groups data and used with aggregate functions - ORDER BY: ordering data in ascending and descending order
how to get first name of employees whose name contains letter'a'	using like
difference between INNER, JOIN, LEFT JOIN, RIGHT JOIN, FULL JOIN	-INNER JOIN: returns only matching rows - LEFT JOIN: returns all rows from left table and matching rows from right - RIGHT JOIN: returns all rows from the right table and matching in left - FULL JOIN: returns all rows from both sides
query to get 2nd largest salary from employees table	select Max(salary) as second_highest_salary from employees where salary<select (max(salary) from employees)
difference between DELETE, TRUNCATE and DROP	-DELETE: deletes specific data from table - TRUNCATE: deletes all data from table - DROP: deletes data and table structure
query to detect duplicate email addresses in users table	group by and having clause
counts grouped by a column	using count() aggregate and group by clause
validate api responses against database values	inspect http status code, check response headers and content, verify data accuracy
write sql queries in automation framework	using prepared statement and statement
subquery	query inside another query
unique and aggregate functions	count, sum, ,min, max, avg +

Created by: tsvete21

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