Are PostgreSQL column names case-sensitive?

Question

I have a db table say, persons in Postgres handed down by another team that has a column name say, \"first_Name\". Now am trying to use PG commande

Answer 1

All identifiers (including column names) that are not double-quoted are folded to lower case in PostgreSQL. Column names that were created with double-quotes and thereby retained upper-case letters (and/or other syntax violations) have to be double-quoted for the rest of their life: ("first_Name")

So, yes, PostgreSQL column names are case-sensitive:

SELECT * FROM persons WHERE "first_Name" = 'xyz';

Also fix the incorrect double-quotes around 'xyz'. Values (string literals) are enclosed in single quotes.

Read the manual here.

My standing advice is to use legal, lower-case names exclusively so double-quoting is not needed.

Answer 2

To quote the documentation:

Key words and unquoted identifiers are case insensitive. Therefore:

UPDATE MY_TABLE SET A = 5;

can equivalently be written as:

uPDaTE my_TabLE SeT a = 5;

You could also write it using quoted identifiers:

UPDATE "my_table" SET "a" = 5;

Quoting an identifier makes it case-sensitive, whereas unquoted names are always folded to lower case (unlike the SQL standard where unquoted names are folded to upper case). For example, the identifiers FOO, foo, and "foo" are considered the same by PostgreSQL, but "Foo" and "FOO" are different from these three and each other.

If you want to write portable applications you are advised to always quote a particular name or never quote it.

Answer 3

The column names which are mixed case or uppercase have to be double quoted in PostgresQL. So best convention will be to follow all small case with underscore.