I want to select the column which has 4th character is number.
example:
column
----------
Game1234
nothing12
demo:db<>fiddle
SELECT
*
FROM
mytable
WHERE substring(col, 4, 1) ~ '[0-9]'
substring() extracts a certain substring (in this case from the 4th position a substring with length 1)
~ '[0-9]' checks if the extracted character is a digit (using regular expressions)
More efficient would be:
substr(col, 4, 1) BETWEEN '0' and '9'
Related
Having couple of entries in database table that have multiple line "names" data.
I try to find single newline character from it.
SELECT
id,
strpos ( NAME, E'\n' ) AS Position_of_substring
FROM
problems
WHERE
strpos ( NAME, E'\n' ) > 0;
But it fails for the data that have more than 1 new line character (\n).
ANy way to find "n" number of "\n" in names data.
regexp_matches will emit a row for each match. doc
SELECT
id,
strpos ( NAME, E'\n' ) AS Position_of_substring
FROM
problems p
WHERE
(select count(*) from regexp_matches(p.name,E'\n','g') ) = ?;
This one gives you a list of all indexes with \n in your string. I am not sure if you were expecting this result:
demo:db<>fiddle
SELECT
name,
array_remove( -- 5
(array_agg(sum))::int[], -- 4
length(name) + 1
)
FROM (
-- 3
SELECT
name,
SUM(length(lines) + 1) OVER (PARTITION BY name ORDER BY row_number)
FROM (
-- 2
SELECT
*,
row_number() OVER ()
FROM (
-- 1
SELECT
name,
regexp_split_to_table(name, '\n') as lines
FROM problems
)s
)s
) s
GROUP BY name
Splitting the string at the \n chars. Every split part is now one row in a temporary table.
Adding a row_count to assure the right order of the split parts
This counts the length of all single split parts. The (length + 1) gives the position of the \n. The SUM window function sums up all values within a group (your original text). That's why the order is relevant. For example: The first two parts of "abc\nde\nfgh" have the lengths of 3 and 2. So the breaks are at 4 (abc = 3, + 1) and 3 (de = 2, + 1). But the 3 of the second part is no real index, but if you sum up these values you get the right indexes: 4 and 7.
Aggregating these results
If (as in my example) the last char is always a \n and you are only interested in the \n chars the string you could remove the last entry of the aggregated array.
Changed problem in comments below:
Would like to replace \n with spaces. So I am thinking how above query
will look in the Update statement. – Pranav Unde
Replacing the \n by spaces is a quiet different problem then getting indexes for all occurances of a special character. And it's much simpler:
UPDATE problems
SET name = trim(regexp_replace(name, E'\n', ' ', 'g'));
regexp_replace(..., 'g') finds all occurances of \n and does the replacing
trim() removes the whitespaces before and after the string if necessary (maybe because there was a trailing \n as in my example - which was replaced by a space as well in the step before)
demo:db<>fiddle
I have a string X-99-XX-999 in postgres 9.6. I'm looking to extract XX. The XX is always between the second and the third hyphen. Can anyone please help?
Use the function split_part()
select split_part('X-99-XX-999', '-', 3)
split_part
------------
XX
(1 row)
From the documentation:
split_part(string text, delimiter text, field int)
Split string on delimiter and return the given field (counting from one)
Example
I have a string...
'/this/is/a/given/string/test.file'.
How can I get substring 'given/string/test.file' in PSQL?
Thank you!
You can use a regular expression
with example(str) as (
values('/this/is/a/given/string/test.file')
)
select regexp_replace(str, '(/.*?){4}', '')
from example;
regexp_replace
------------------------
given/string/test.file
(1 row)
or the function string_to_array():
select string_agg(word, '/' order by ord)
from example,
unnest(string_to_array(str, '/')) with ordinality as u(word, ord)
where ord > 4;
Read also How to find the 3rd occurrence of a pattern on a line.
I dont know how to get the nth occurence of a substring, but for this problem, you can use regular expression. Like this:
select substring('/this/is/a/given/string/test.file' from '/[^/]+/[^/]+/[^/]+/(.*)')
You can improve the regular expression, this is just for demo purpose.
I'm working with PostgreSQL and want to know whether you can have a wildcard retain its value.
So for example say I had
select * from tableOne where field like ‘_DEF_’;
Is there a way to get the first and last wildcard to be the exact same character?
So an example matching result could be: ADEFA or ZDEFZ.
You can use a regular expression with a back-reference:
select *
from some_table
where some_column ~* '^(.)DEF(\1)$'
^(.)DEF(\1)$ means: some character at the beginning followed DEF followed by the first character must occur at the end of the string.
The () defines a group and the \1 references the first group (which is the first character in the input sequence in this example)
SQLFiddle example: http://sqlfiddle.com/#!15/d4c4d/1
Use regular expression:
with test as (
select 'xABa' as foo
union select 'xABx'
union select 'xJBx'
)
select * from test
where foo ~* E'^(.)AB\\1$'
Outputs:
foo
------
xABx
(1 row)
I need to remove non-numeric characters in a column (character varying) and keep numeric values in postgresql 9.3.5.
Examples:
1) "ggg" => ""
2) "3,0 kg" => "3,0"
3) "15 kg." => "15"
4) ...
There are a few problems, some values are like:
1) "2x3,25"
2) "96+109"
3) ...
These need to remain as is (i.e when containing non-numeric characters between numeric characters - do nothing).
Using regexp_replace is more simple:
# select regexp_replace('test1234test45abc', '[^0-9]+', '', 'g');
regexp_replace
----------------
123445
(1 row)
The ^ means not, so any character that is not in the range 0-9 will be replaced with an empty string, ''.
The 'g' is a flag that means all matches will be replaced, not just the first match.
For modifying strings in PostgreSQL take a look at The String functions and operators section of the documentation. Function substring(string from pattern) uses POSIX regular expressions for pattern matching and works well for removing different characters from your string.
(Note that the VALUES clause inside the parentheses is just to provide the example material and you can replace it any SELECT statement or table that provides the data):
SELECT substring(column1 from '(([0-9]+.*)*[0-9]+)'), column1 FROM
(VALUES
('ggg'),
('3,0 kg'),
('15 kg.'),
('2x3,25'),
('96+109')
) strings
The regular expression explained in parts:
[0-9]+ - string has at least one number, example: '789'
[0-9]+.* - string has at least one number followed by something, example: '12smth'
([0-9]+.\*)* - the string similar to the previous line zero or more times, example: '12smth22smth'
(([0-9]+.\*)*[0-9]+) - the string from the previous line zero or more times and at least one number at the end, example: '12smth22smth345'