Populating a table in PostgreSQL with one million records of random data.

create table my_table_1(a bigint, b varchar(1000), c timestamp, d bool, e float);

INSERT INTO my_table_1 (a, b, c, d, e)
SELECT
 (random() * 10000)::bigint, -- generates a random integer between 0 and 10,000, which is cast to a bigint 
 ARRAY_TO_STRING(ARRAY(SELECT chr((65 + (random() * 25))::int) FROM generate_series(1, (1000*random())::int)), ''), -- generates a random string of characters of variable length, where each character is an uppercase letter (A-Z), and concatenates them into a single string without any delimiter.
 NOW() - random() * INTERVAL '365 days', -- generates a random date within the past year 
 random() < 0.5, -- generates a random boolean value (true or false) 
 random() * 100 -- generates a random floating-point number between 0 and 100
FROM generate_series(1, 1000000);

select count(1) from my_table_1;

select d, count(1) from my_table_1 group by 1;