Add LIMIT, OFFSET and TIES post #70
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| `LIMIT` / `FETCH FIRST ... ROWS ONLY`, `FETCH FIRST ... WITH TIES` and `OFFSET` are powerful and very useful clauses | ||
| that come especially handy when writing ad-hoc queries over big data sets. Since semantics of these clauses depend on query | ||
| results being well ordered, they are best used with `ORDER BY` that defined proper ordering. Without proper ordering |
| If we look again at the database systems mentioned above, it turns out many of them support the standard | ||
| syntax too: Oracle, DB2, SQL Server and PostgreSQL (although that's not documented currently). | ||
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| And Presto? Presto has `LIMIT n` support since 2012. In [Presto 310](https://prestosql.io/docs/current/release/release-310.html), |
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IMO "310" is not sufficient for describing link target.
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This renders as:
And Presto? Presto has LIMIT n support since 2012. In Presto 310, Presto gained also the FETCH FIRST n ROWS ONLY support.
Too much "Presto".
Maybe "Since 310, Presto gained..."
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Right. "In Presto 310, we added ..."
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| The `FETCH FIRST n ROWS WITH TIES` clause retains all rows with equal values of the ordering keys (the `ORDER BY` clause) as | ||
| the last row that would be returned by the `FETCH FIRST n ROWS ONLY` clause (or its equivalent, `LIMIT n`). |
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| Per the SQL Standard, the `FETCH FIRST n ROWS ONLY` clause can be prepended with `OFFSET m`, to skip `m` initial rows. | ||
| In such a case, it makes sense to use `FETCH NEXT ...` variant of the clause -- it's allowed with and without `OFFSET`, | ||
| but definitely looks better with that clause. |
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skip " -- it's allowed...". It makes the piece harder to read.
There are more variants of the clause not mentioned in this post.
Optionally, you could describe all of them in one place in grammar-like style:
FETCH (FIRST | NEXT) n? (ROW | ROWS) (ONLY | WITH TIES)
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I will keep this, but will also add ref to docs which describe full grammar
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