Postgresql pattern match string columns for a number

Question

Given a table of measurements as strings (i.e. "4.6 Inches, 3mm", "Length: 4.66in", etc), I'd like to retrieve rows with essentially anything left or right of the number, so long as the number matches.

In other words, if I'm searching for "6":

match: "6 in", "6in", "asdf 6 in", etc
don't match: "16 in", "6.6 in", "with 66 in", etc

I have the following query thus far:

select distinct length from items where length ~ '[[:<:]]6[[:>:]]';

But it's not quite what I'm looking for, as this is the result:

     length      
---------------
 6.25 Inches
 4.6666 Inches
 6.5 Inches
 1.66 Inches
 6 Inches
 6.75 Inches
 6.71 Inches
 24.6 Inches
 3.6666 Inches

I'm using PostgreSQL 9. Any help would be appreciated. Thanks

Draco Ater · Accepted Answer · 2011-05-25 20:13:55Z

1

As I understood, you want exact number match in string. So the number (6 in your case) cannot be surrounded by numerics or decimal sign. So the regex should look like that:

[^0-9\.]6[^0-9\.]

You can change the 6, to any number you are looking for.

answered May 25, 2011 at 20:13

Draco Ater

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Toto · Accepted Answer · 2011-05-26 09:23:08Z

0

How about :

'^[^0-9]*6[^0-9]*$'

answered May 26, 2011 at 9:23

Toto

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Seth Robertson · Accepted Answer · 2011-05-25 20:11:09Z

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create table foo (length text);
insert into foo values ('6 in'), ('asdf 6 in'), ('6in'), ('16 in'), ('6.6 in'), ('6.6'), ('with 66 in');
select distinct length from foo where length ~ '[^0-9 .][0-5.7-9 ]*6|6*[0-5.7-9 ]*[^0-9 .]';

Edited to work correctly with ' 6 ' and '6.6'.

answered May 25, 2011 at 20:11

Seth Robertson

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Denis de Bernardy · Accepted Answer · 2011-05-25 20:22:17Z

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No offense, but storing this as a varchar is not a good idea.

This should be stored as two separate fields (quantity / units), or (better yet) a single field (quantity with a predefined unit, e.g. mm), and queried accordingly.

answered May 25, 2011 at 20:22

Denis de Bernardy

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1 Comment

Lock Reck Over a year ago

Absolutely agree. Problem is the data came from an outside source in this format and it would need to be split, thus the need for this pattern matcher.

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