What is the ~ operator?

What is true regarding file system backup?

To backup a database, the postmaster daemon must be halted.

SELECT !!3; What output will this statement give?

SELECT 'infinity'::timestamp;

Will this statement produce an error?

While creating a trigger, the function it will call may be created after it and attached to it

SELECT rtrim('foobar', 'abr');

The result of this statement is foo.

Which kind of index can be declared unique?

What i s the difference between tokens and lexemes?

SELECT 'infinity'::timestamp;

Will this statement produce an error?

The following statement will retrieve the second element of the array column products in table store_products.

SELECT products[1] FROM store_products;