CURRENT_DATE, CURRENT_TIMESTAMP, NOW() in PostgreSQL - Step-by-Step Execution

Concept Flow - CURRENT_DATE, CURRENT_TIMESTAMP, NOW()

Start Query

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Evaluate CURRENT_DATE

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Evaluate CURRENT_TIMESTAMP

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Evaluate NOW()

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Return Results

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End Query

The query evaluates CURRENT_DATE, CURRENT_TIMESTAMP, and NOW() functions step-by-step, returning the current date or timestamp values.

Execution Sample

PostgreSQL

SELECT CURRENT_DATE, CURRENT_TIMESTAMP, NOW();

This query returns the current date, the current timestamp with timezone, and the current timestamp with timezone again.

Execution Table

Step	Function Evaluated	Result Type	Result Example	Notes
1	CURRENT_DATE	date	2024-06-15	Returns only the date part, no time included
2	CURRENT_TIMESTAMP	timestamp with time zone	2024-06-15 14:23:45.123456+00	Returns date and time with timezone
3	NOW()	timestamp with time zone	2024-06-15 14:23:45.123456+00	Equivalent to CURRENT_TIMESTAMP
4	Return Results	row	(2024-06-15, 2024-06-15 14:23:45.123456+00, 2024-06-15 14:23:45.123456+00)	Query returns all three values as one row

💡 All functions evaluated and results returned as a single row.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
CURRENT_DATE	NULL	2024-06-15	2024-06-15	2024-06-15	2024-06-15
CURRENT_TIMESTAMP	NULL	NULL	2024-06-15 14:23:45.123456+00	2024-06-15 14:23:45.123456+00	2024-06-15 14:23:45.123456+00
NOW()	NULL	NULL	NULL	2024-06-15 14:23:45.123456+00	2024-06-15 14:23:45.123456+00

Key Moments - 3 Insights

Why does CURRENT_DATE return only the date without time?

CURRENT_DATE is designed to return only the date part, as shown in execution_table step 1, so it excludes time information.

Are CURRENT_TIMESTAMP and NOW() different in their output?

No, both CURRENT_TIMESTAMP and NOW() return the current date and time with timezone, as shown in execution_table steps 2 and 3, they produce the same result.

Why do CURRENT_TIMESTAMP and NOW() include timezone information?

Because they return 'timestamp with time zone' type, which includes timezone data to represent the exact moment globally, as seen in execution_table steps 2 and 3.

Visual Quiz - 3 Questions

Look at the execution_table, what type of value does CURRENT_DATE return at step 1?

A Timestamp with timezone

B Timestamp without timezone

C Date only

D Time only

💡 Hint

Check the 'Result Type' column in execution_table row 1.

At which step do CURRENT_TIMESTAMP and NOW() produce the same result?

A Step 2 and Step 3

B Step 4

C Step 1

D They never produce the same result

💡 Hint

Look at the 'Result Example' and 'Notes' columns for steps 2 and 3 in execution_table.

If you only want the current date without time, which function should you use?

A CURRENT_TIMESTAMP

B CURRENT_DATE

C NOW()

D All return the same

💡 Hint

Refer to the 'Result Type' and 'Notes' for CURRENT_DATE in execution_table step 1.

Concept Snapshot

CURRENT_DATE returns the current date only (no time).
CURRENT_TIMESTAMP returns current date and time with timezone.
NOW() is equivalent to CURRENT_TIMESTAMP.
Use CURRENT_DATE for date only, NOW() or CURRENT_TIMESTAMP for full timestamp.
All return values reflect the moment the query runs.

Full Transcript

This visual execution trace shows how PostgreSQL evaluates CURRENT_DATE, CURRENT_TIMESTAMP, and NOW() functions in a query. First, CURRENT_DATE returns only the date part without time. Then, CURRENT_TIMESTAMP returns the current date and time including timezone information. NOW() returns the same timestamp as CURRENT_TIMESTAMP. The query returns all three values as one row. Beginners often wonder why CURRENT_DATE excludes time and why CURRENT_TIMESTAMP and NOW() are the same; this trace clarifies those points by showing each step and the resulting values. Use CURRENT_DATE when you want just the date, and use NOW() or CURRENT_TIMESTAMP when you need the full timestamp with timezone.