[Q] Update from a table

Ladislav Lenart <lenartlad@volny.cz> writes:

What happens if I issue UPDATE SET FROM... but with incomplete/buggy WHERE
condition and thus SEVERAL rows from the from_list match ONE row to update?

Any given row will be updated at most once. However, the from_list row
it gets updated against will be unpredictable, depending on the
implementation of the join.

regards, tom lane

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On 5.12.2013 15:14, Tom Lane wrote:

Ladislav Lenart <lenartlad@volny.cz> writes:

What happens if I issue UPDATE SET FROM... but with incomplete/buggy WHERE
condition and thus SEVERAL rows from the from_list match ONE row to update?

Any given row will be updated at most once. However, the from_list row
it gets updated against will be unpredictable, depending on the
implementation of the join.

regards, tom lane

Makes perfect sense.

Thank you,

Ladislav Lenart

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