SELECT column name starting with numeral-CodePudding

This one is out of morbid curiosity. I have a very badly named table here:

CREATE TABLE badtable (
    id INT PRIMARY KEY,
    "customer name" VARCHAR(63),
    "order" VARCHAR(12),
    "1st" date,
    "last-date" date
);

I am trying to show when you might desperately need delimited column names. However, the following is not an error:

SELECT
    "customer name",
    "order",
    1st,    --  no delimiter
    "last-date"
FROM badtable;

Instead it happily gives me a column called st.

This works on both PostgreSQL and Microsoft SQL Server, so it’s not limited to a quirk of one of them.

How is the 1st column name being interpreted?

CodePudding user response：

In some situations whitespace is not required as long as the DBMS is able to read the expression unambiguously.

select 1st

selects a 1. What follows is the alias name. Hence the same as

select 1 st

select 1 as st