TO_DATE and TO_TIMESTAMP for parsing in PostgreSQL - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the TO_DATE function do in PostgreSQL?

TO_DATE converts a string into a date type using a specified format.

It helps turn text like '2024-06-01' into a real date the database understands.

beginner

How is TO_TIMESTAMP different from TO_DATE?

TO_TIMESTAMP converts a string into a timestamp, including date and time parts.

TO_DATE only converts to a date without time.

beginner

Example: What does TO_DATE('31-12-2023', 'DD-MM-YYYY') return?

It returns the date 2023-12-31 as a date type.

The format 'DD-MM-YYYY' tells PostgreSQL how to read the string.

intermediate

Why do you need to specify a format string in TO_DATE or TO_TIMESTAMP?

The format string tells PostgreSQL how to read the parts of the date/time in the text.

Without it, PostgreSQL might misunderstand the order or meaning of day, month, year, hour, etc.

intermediate

What happens if the input string does not match the format in TO_DATE?

PostgreSQL will raise an error because it cannot correctly parse the string into a date.

Always ensure the string matches the format exactly.

Which function converts a string to a timestamp including time information?

A NOW()

B TO_DATE

C CAST

D TO_TIMESTAMP

TO_TIMESTAMP converts strings to timestamps with date and time.

What does TO_DATE('2024/06/01', 'YYYY/MM/DD') return?

A A timestamp value for June 1, 2024

B A date value for June 1, 2024

C An error because of wrong format

D A string '2024/06/01'

The function returns a date because the string matches the format.

If you want to parse '15:30:00' as time only, which function is best?

A TO_TIMESTAMP

B TO_DATE

C TO_TIME

D CAST

TO_TIMESTAMP can parse time parts; TO_DATE cannot.

What format string matches '31-12-2023'?

A MM-DD-YYYY

B YYYY-MM-DD

C DD-MM-YYYY

D YYYY-DD-MM

Day first, then month, then year matches '31-12-2023'.

What happens if the input string is '2023-31-12' but format is 'YYYY-MM-DD'?

A Error due to mismatch

B Parsed correctly

C Returns NULL

D Returns current date

Format and string must match exactly or an error occurs.

Explain how to use TO_DATE to convert a string into a date in PostgreSQL.

Think about how you tell PostgreSQL the order of day, month, and year.

Describe the difference between TO_DATE and TO_TIMESTAMP and when to use each.

Consider if you need hours and minutes or just the day.