From: | 毛毛 <krave(at)163(dot)com> |
---|---|
To: | pgsql-general(at)lists(dot)postgresql(dot)org |
Subject: | How can I accurately infer the output of a SELECT statement FROM a table with floating-point data type? |
Date: | 2023-10-19 03:45:54 |
Message-ID: | 10b02a08.28b4.18b460a2f09.Coremail.krave@163.com |
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Lists: | pgsql-general |
Hi,
Do we have a rule by follow which one can accurately info the output of a SELECT statment FROM a table with floating-point data type?
I am working with PostgreSQL 16 and pgAdmin 7.6.
Here is my SQL script:
```
CREATE TABLE TEST (REAL_COLUMN real);
INSERT INTO TEST
VALUES (12345.123456789);
SELECT * FROM TEST;
```
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
So I thought the output of the SELECT statement should be like: 12345.1 with 6 digits in total.
But it turns out to be 12345.123 with 8 digits in total.
May I know why would this happen?
Do we have a rule I can use to infer the correct output of a floating-point number without running the script?
Thank you for your time and have a great day!
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