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SQL EXERCISES
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SQL | Looping exercise | Find first n primes using looping
This exercise is provided to allow potential course delegates to choose the correct Wise Owl Microsoft training course, and may not be reproduced in whole or in part in any format without the prior written consent of Wise Owl.
The answer to the exercise will be included and explained if you attend one of more of the courses listed below!
| Software ==> | SQL (198 exercises) |
| Version ==> | Any version of SQL Server |
| Topic ==> | Looping (3 exercises) |
| Level ==> | Harder than average |
| Courses ==> | Fast-track SQL / Advanced SQL |
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Your task is to write a query to show the first (say) 1000 primes. Here's a suggested algorithm:
- Create an integer variable to hold the value whose primeness you're testing
- Use WHILE to loop until this integer is 1000, incrementing its value by 1 each time round the loop (let's call this number P)
Within this outer loop:
- Find out the square root of the number you're testing (use SQRT)
- Find out what the highest integer is just below this (use FLOOR) - let's call this X
- Try dividing each number from 1 up to and including X into P
- If we ever find a number such that P % X = 0 (ie that P leaves a remainder of 0 when divided by X) we have a non-prime, and we should flag this accordingly and break out of the loop
If it helps, here's what you should see to start with:
The first few primes!
If you get this working, try incorporating a timestamp to see how long it took to run:
The start of the time test - at the end, set @EndTime and use DateDiff(ms, @StartTime, @EndTime) to work out the difference in milliseconds
Save your hard work as Printing primes.sql, then close it down!