Sampling a Table
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Go to this page Sampling a Table
(Created page with "Getting a few random rows from as Oracle Database table can be done in many different ways. This will just select the first ten rows Oracle comes across in the table: <pre> ...") |
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where | where | ||
rownum<=10 | rownum<=10 | ||
| - | |||
</pre> | </pre> | ||
They are likely to all be inserted at a similar time and therefore all similar. If you need a cross section: | They are likely to all be inserted at a similar time and therefore all similar. If you need a cross section: | ||
| + | <pre> | ||
| + | select * | ||
| + | from iso_country | ||
| + | sample (10) -- percentage of rows to display | ||
| + | </pre> | ||
| + | |||
| + | The percentage of rows is not precise, there are 249 rows in the sample iso_country table, but the 10% sample count has given a range from 15 - 31 rows: | ||
| + | |||
| + | <pre> | ||
| + | select count(*) | ||
| + | from iso_country | ||
| + | sample (10) -- percentage of rows to display | ||
| + | </pre> | ||
| + | |||
| + | Additional conditions can be added to a sampling query, but they appear to be applied after the original sample has been taken, so there is no guarantee that the query will show any rows: | ||
| + | <pre> | ||
| + | select * | ||
| + | from iso_country | ||
| + | sample (10) | ||
| + | where code like 'A%' | ||
| + | </pre> | ||
