| From: | "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> |
|---|---|
| To: | 毛毛 <krave(at)163(dot)com> |
| Cc: | "pgsql-general(at)lists(dot)postgresql(dot)org" <pgsql-general(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: How can I accurately infer the output of a SELECT statement FROM a table with floating-point data type? |
| Date: | 2023-10-19 04:14:47 |
| Message-ID: | CAKFQuwb7Dbsm-hDmJzCJ+ApipD7p-wqRunY5yqVCEq3AjYsxpA@mail.gmail.com |
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| Lists: | pgsql-general |
On Wednesday, October 18, 2023, 毛毛 <krave(at)163(dot)com> wrote:
>
>
> I consulted the following doc and found that the range of real type is 6
> decimal digits precision.
> https://www.postgresql.org/docs/current/datatype-numeric.
> html#DATATYPE-NUMERIC
>
You also need to consult:
https://www.postgresql.org/docs/current/datatype-numeric.html#DATATYPE-FLOAT
But in short, no, the result is input specific and you the user are not
expected to know or care about such details. The docs say you will get
between 6 and 9 digits depending on the value, under default settings. The
table gives the minimum as clarified in the prose. There is room in the
table to include more detail and it probably should.
David J.
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