Question

The below Postgres SQL query is returning all records available in the table.
Can someone give explanation for this? .
Also please let me know what * represents in case of postgres regular expression.

Employee table contains :

name
Chennai
Delhi
Hydrabad
NewYark
ABC

select * from employee where name ~ 'Z*'

Answer 1

The * quantifier means zero or more. Since every name contains at least zero Z characters, every row is returned.

You don’t need to use a regex to find strings starting with a character, you can just use LIKE:

SELECT record FROM myrecords WHERE name LIKE 'Z%';

If you want names starting with Z using a regex, try this:

SELECT record FROM myrecords WHERE name ~ '^Z';

If you want names containing at least one Z, try one of these:

SELECT record FROM myrecords WHERE name LIKE '%Z%';
SELECT record FROM myrecords WHERE name ~ 'Z';