docs(ASOF JOIN): Clarify timestamp control and precedence #197
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it was confusing before
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🚀 Build success! Latest successful preview: https://preview-197--questdb-documentation.netlify.app/docs/ Commit SHA: a17d08a
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goodroot
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Jun 9, 2025
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| :::caution | ||
| #### The Default Behavior: Implicit Timestamp Propagation |
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This title is slightly long.
Consider:
#### Default behaviour
As a default, QuestDB appies implicit timestamp propogation. This means that by default, an `ASOF JOIN` will...
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I wanted to be verbose here since I saw people getting this wrong and explicitly marking a column as a designated timestamp
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| ```questdb-sql | ||
| ```questdb-sql title="ASOF JOIN with designated timestamp" |
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unfortunately no:(
in fact, I found a bug while trying to find an equivalent demo-able query 😬
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| Example: Joining on `ingestion_time` instead of the default `trade_ts` | ||
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| ```questdb-sql title="ASOF JOIN with custom timestamp" |
Co-authored-by: goodroot <[email protected]>
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Rework the
ASOF JOINtimestamp documentation to address the common misuse of thetimestamp(ts)syntax.The guide now clarifies that the designated timestamp is inherited by default. The standard method for joining on a different column is to use an
ORDER BYclause in a subquery, which implicitly sets a new timestamp for the join.The
timestamp(ts)syntax is now correctly framed as an expert-level performance hint, used only to assert a pre-sorted order on data that lacks a designated timestamp.