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: 62d4145
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goodroot
reviewed
Jun 9, 2025
| @@ -327,30 +327,86 @@ Result: | |||
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| </div> | |||
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| ### Timestamp considerations | |||
| ### How ASOF JOIN Uses Timestamps | |||
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| ### How ASOF JOIN Uses Timestamps | |
| ### How ASOF JOIN uses timestamps |
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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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| ```questdb-sql | ||
| ```questdb-sql title="ASOF JOIN with designated timestamp" |
| ``` | ||
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| #### The Standard Override Method: Using ORDER BY |
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| #### The Standard Override Method: Using ORDER BY | |
| #### Using ORDER BY |
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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" |
| ASOF JOIN quotes ON (symbol); | ||
| ``` | ||
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| #### Using the timestamp() Syntax |
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| #### Using the timestamp() Syntax | |
| #### Using the timestamp() syntax |
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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.