How to make "case-insensitive" query in Postgresql? - postgresql

Question

Is there any way to write case-insensitive queries in PostgreSQL, E.g. I want that following 3 queries return same result.
SELECT id FROM groups where name='administrator'
SELECT id FROM groups where name='ADMINISTRATOR'
SELECT id FROM groups where name='Administrator'

Answer 1

Use LOWER function to convert the strings to lower case before comparing.
Try this:
SELECT id
FROM groups
WHERE LOWER(name)=LOWER('Administrator')

Answer 2

using ILIKE instead of LIKE
SELECT id FROM groups WHERE name ILIKE 'Administrator'

Answer 3

The most common approach is to either lowercase or uppercase the search string and the data. But there are two problems with that.
It works in English, but not in all languages. (Maybe not even in
most languages.) Not every lowercase letter has a corresponding
uppercase letter; not every uppercase letter has a corresponding
lowercase letter.
Using functions like lower() and upper() will give you a sequential
scan. It can't use indexes. On my test system, using lower() takes
about 2000 times longer than a query that can use an index. (Test data has a little over 100k rows.)
There are at least three less frequently used solutions that might be more effective.
Use the citext module, which mostly mimics the behavior of a case-insensitive data type. Having loaded that module, you can create a case-insensitive index by CREATE INDEX ON groups (name::citext);. (But see below.)
Use a case-insensitive collation. This is set when you initialize a
database. Using a case-insensitive collation means you can accept
just about any format from client code, and you'll still return
useful results. (It also means you can't do case-sensitive queries. Duh.)
Create a functional index. Create a lowercase index by using CREATE
INDEX ON groups (LOWER(name));. Having done that, you can take advantage
of the index with queries like SELECT id FROM groups WHERE LOWER(name) = LOWER('ADMINISTRATOR');, or SELECT id FROM groups WHERE LOWER(name) = 'administrator'; You have to remember to use LOWER(), though.
The citext module doesn't provide a true case-insensitive data type. Instead, it behaves as if each string were lowercased. That is, it behaves as if you had called lower() on each string, as in number 3 above. The advantage is that programmers don't have to remember to lowercase strings. But you need to read the sections "String Comparison Behavior" and "Limitations" in the docs before you decide to use citext.

Answer 4

You can use ILIKE. i.e.
SELECT id FROM groups where name ILIKE 'administrator'

Answer 5

You can also read up on the ILIKE keyword. It can be quite useful at times, albeit it does not conform to the SQL standard. See here for more information: http://www.postgresql.org/docs/9.2/static/functions-matching.html

Answer 6

You could also use POSIX regular expressions, like
SELECT id FROM groups where name ~* 'administrator'
SELECT 'asd' ~* 'AsD' returns t

Answer 7

use ILIKE
select id from groups where name ILIKE 'adminstration';
If your coming the expressjs background and name is a variable
use
select id from groups where name ILIKE $1;

Answer 8

Using ~* can improve greatly on performance, with functionality of INSTR.
SELECT id FROM groups WHERE name ~* 'adm'
return rows with name that contains OR equals to 'adm'.

Answer 9

ILIKE work in this case:
SELECT id
FROM groups
WHERE name ILIKE 'Administrator'

Answer 10

For a case-insensitive parameterized query, you can use the following syntax:
"select * from article where upper(content) LIKE upper('%' || $1 || '%')"

Answer 11

-- Install 'Case Ignore Test Extension'
create extension citext;
-- Make a request
select 'Thomas'::citext in ('thomas', 'tiago');
select name from users where name::citext in ('thomas', 'tiago');

Answer 12

If you want not only upper/lower case but also diacritics, you can implement your own func:
CREATE EXTENSION unaccent;
CREATE OR REPLACE FUNCTION lower_unaccent(input text)
RETURNS text
LANGUAGE plpgsql
AS $function$
BEGIN
return lower(unaccent(input));
END;
$function$;
Call is then
select lower_unaccent('Hôtel')
>> 'hotel'

Answer 13

A tested approach is using ~*
As in the example below
SELECT id FROM groups WHERE name ~* 'administrator'

Answer 14

select id from groups where name in ('administrator', 'ADMINISTRATOR', 'Administrator')