Date, time, and timestamp types in PostgreSQL - Step-by-Step Execution

Concept Flow - Date, time, and timestamp types

Start: Input Date/Time Value

↓

Check Data Type

↓

Date

↓

Store in DB

↓

Retrieve & Format

↓

Output

The flow shows how input values are checked for type (date, time, timestamp), stored, and then retrieved formatted.

Execution Sample

PostgreSQL

CREATE TABLE events (
  event_date DATE,
  event_time TIME,
  event_timestamp TIMESTAMP
);

INSERT INTO events VALUES ('2024-06-01', '14:30:00', '2024-06-01 14:30:00');

SELECT * FROM events;

This code creates a table with date, time, and timestamp columns, inserts one row, and selects all rows.

Execution Table

Step	Action	Input Value	Data Type Detected	Stored Value	Output on SELECT
1	Create table with date, time, timestamp columns	N/A	N/A	Table schema created	N/A
2	Insert row with '2024-06-01', '14:30:00', '2024-06-01 14:30:00'	2024-06-01, 14:30:00, 2024-06-01 14:30:00	Date, Time, Timestamp	Stored as date, time, timestamp	N/A
3	Select all rows from events	N/A	N/A	N/A	event_date: 2024-06-01, event_time: 14:30:00, event_timestamp: 2024-06-01 14:30:00
4	End of execution	N/A	N/A	N/A	Query complete, all data retrieved

💡 All rows processed and output displayed

Variable Tracker

Variable	Start	After Insert	After Select	Final
event_date	NULL	2024-06-01	2024-06-01	2024-06-01
event_time	NULL	14:30:00	14:30:00	14:30:00
event_timestamp	NULL	2024-06-01 14:30:00	2024-06-01 14:30:00	2024-06-01 14:30:00

Key Moments - 3 Insights

Why does '2024-06-01' store differently in DATE and TIMESTAMP columns?

DATE stores only the date part without time, while TIMESTAMP stores both date and time. See execution_table row 2 where data types differ.

What happens if you insert a time value into a DATE column?

PostgreSQL will reject it or truncate time part because DATE only accepts date values. This is why data types must match as shown in row 2.

Why does SELECT show the full timestamp including time?

Because TIMESTAMP stores both date and time, SELECT outputs the full value as in row 3.

Visual Quiz - 3 Questions

Look at the execution_table, what is the stored value for event_time after the insert step?

A 2024-06-01 14:30:00

B 2024-06-01

C 14:30:00

D NULL

💡 Hint

Check the 'Stored Value' column in execution_table row 2 for event_time

At which step does the SELECT query output the full timestamp?

A Step 3

B Step 1

C Step 2

D Step 4

💡 Hint

Look at the 'Output on SELECT' column in execution_table row 3

If you tried to insert '14:30:00' into event_date, what would happen?

A It stores as '2024-06-01' in event_date

B Insertion fails due to type mismatch

C It stores as '14:30:00' in event_date

D It stores as NULL

💡 Hint

Refer to key_moments about type mismatch on insert

Concept Snapshot

PostgreSQL date/time types:
- DATE stores only date (YYYY-MM-DD)
- TIME stores only time (HH:MM:SS)
- TIMESTAMP stores date and time (YYYY-MM-DD HH:MM:SS)
Insert values must match column type
SELECT returns stored values formatted accordingly

Full Transcript

This visual execution shows how PostgreSQL handles date, time, and timestamp types. First, a table is created with columns for each type. Then, a row is inserted with matching values: a date string for DATE, a time string for TIME, and a combined date-time string for TIMESTAMP. The execution table traces each step: creation, insertion, and selection. Variables track how values change from NULL to stored data. Key moments clarify common confusions like why date and timestamp differ and what happens on type mismatch. The quiz tests understanding of stored values and behavior on insert and select. The snapshot summarizes the core rules for these types in PostgreSQL.