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Today, for fun, I wrote prime number generation upto 1000 using pure single MySQL query.
No already created tables, no procedures, no variables. Just pure SQL using derived tables.
So does this mean that pure SQL statements do not have the halting problem?
Putting an EXPLAIN over the query I could see how MySQL guessed that the total number of calculations would be 1000*1000 even before executing the query in itself and this is amazing ♥️
I have attached a screenshot of the query and if you are curious, I have also left below the plain text.
PS this was a SQL problem in Hackerrank.
MySQL query:
select group_concat(primeNumber SEPARATOR '&') from
(select numberTable.number as primeNumber from
(select cast((concat(tens, units, hundreds)+1) as UNSIGNED) as number from
(select 0 as units union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) unitsTable,
(select 0 as tens union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) tensTable,
(select 0 as hundreds union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) hundredsTable order by number) numberTable
inner join
(select cast((concat(tens, units, hundreds)+1) as UNSIGNED) as divisor from
(select 0 as units union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) unitsTable,
(select 0 as tens union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) tensTable,
(select 0 as hundreds union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) hundredsTable order by divisor) divisorTable
on (divisorTable.divisor<=numberTable.number and divisorTable.divisor!=1)
where numberTable.number%divisorTable.divisor=0
group by numberTable.number having count(*)<=1 order by numberTable.number) resultTable;
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Here’s a poster with a super short description of each one to help you keep track and find some new useful Linux tools.
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