CURRENT_DATE, CURRENT_TIMESTAMP, NOW() in PostgreSQL - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the CURRENT_DATE function return in PostgreSQL?

CURRENT_DATE returns the current date from the system clock without the time part. It shows the year, month, and day only.

beginner

How is CURRENT_TIMESTAMP different from CURRENT_DATE?

CURRENT_TIMESTAMP returns the current date and time including hours, minutes, seconds, and fractional seconds, while CURRENT_DATE returns only the date.

beginner

What does the NOW() function return in PostgreSQL?

NOW() returns the current date and time, similar to CURRENT_TIMESTAMP. It shows the exact moment the query runs.

intermediate

Can CURRENT_TIMESTAMP and NOW() return different values in the same query?

No, both CURRENT_TIMESTAMP and NOW() return the same timestamp value within a single query execution because they use the transaction start time.

beginner

Why might you use CURRENT_DATE instead of CURRENT_TIMESTAMP or NOW()?

You use CURRENT_DATE when you only need the date without the time, for example, to record birthdays or due dates where time is not important.

Which function returns only the date part without time in PostgreSQL?

A GETDATE()

B CURRENT_TIMESTAMP

C CURRENT_DATE

D NOW()

CURRENT_DATE returns only the date part. CURRENT_TIMESTAMP and NOW() include time. GETDATE() is not standard in PostgreSQL.

What does NOW() return in PostgreSQL?

A Current date and time

B Current time only

C Current date only

D Current timestamp without time zone

NOW() returns the current date and time including hours, minutes, and seconds.

Are CURRENT_TIMESTAMP and NOW() different in PostgreSQL?

A Yes, they return different times

B No, they return the same timestamp

C CURRENT_TIMESTAMP returns date only

D NOW() returns date only

Both return the same timestamp value during a query execution.

If you want to store only the date of a user's birthday, which function is best?

A CURRENT_DATE

B NOW()

C CURRENT_TIMESTAMP

D SYSDATE

CURRENT_DATE returns only the date, which is suitable for birthdays.

Which of these is true about CURRENT_TIMESTAMP in PostgreSQL?

A It returns only the date

B It returns the current system time at call

C It returns a random timestamp

D It returns the time when the query started

CURRENT_TIMESTAMP returns the timestamp at the start of the current transaction or query.

Explain the difference between CURRENT_DATE, CURRENT_TIMESTAMP, and NOW() in PostgreSQL.

Think about what part of the date/time each function returns.

When would you choose to use CURRENT_DATE instead of NOW() in your database queries?

Consider situations where time details are unnecessary.