PostgreSQL LOCALTIME Date/Time Function
PostgreSQL LOCALTIME Date/Time Function
The PostgreSQL LOCALTIME function is used to get the current time of day without time zone. This function can also return the current time with limited precision. It is essential for retrieving the current time for various time-based calculations and comparisons.
Syntax
LOCALTIMEThe LOCALTIME function does not take any arguments and returns a time representing the current time of day without time zone.
LOCALTIME(integer)The LOCALTIME function can also take an integer argument to specify the number of decimal places of precision for the seconds field.
Example PostgreSQL LOCALTIME Queries
Let's look at some examples of PostgreSQL LOCALTIME function queries:
1. Basic LOCALTIME Example
SELECT LOCALTIME AS current_time;
This query retrieves the current time of day without time zone at the moment of execution.
2. LOCALTIME with Limited Precision
SELECT LOCALTIME(0) AS current_time_precise;
This query retrieves the current time of day without time zone at the moment of execution, with the seconds field limited to zero decimal places of precision.
3. LOCALTIME with Column Values
SELECT id, name, LOCALTIME AS query_time
FROM people;
This query retrieves the id, name, and the current time of day without time zone for each row in the people table, capturing the exact time of query execution for each row.
Full Example
Let's go through a complete example that includes creating a table, inserting data, and using the LOCALTIME function to capture the current time at various points within a query.
Step 1: Creating a Table
This step involves creating a new table named people to store people's data.
CREATE TABLE people (
id SERIAL PRIMARY KEY,
name TEXT
);
In this example, we create a table named people with columns for id and name.
Step 2: Inserting Data into the Table
This step involves inserting some sample data into the people table.
INSERT INTO people (name)
VALUES ('Alice'),
('Bob'),
('Charlie');
Here, we insert data into the people table.
Step 3: Using the LOCALTIME Function
This step involves using the LOCALTIME function to capture the current time during the execution of queries.
Retrieve current time:
SELECT LOCALTIME AS current_time;
This query retrieves the current time of day without time zone at the moment of execution.
Retrieve current time with limited precision:
SELECT LOCALTIME(0) AS current_time_precise;
This query retrieves the current time of day without time zone at the moment of execution, with the seconds field limited to zero decimal places of precision.
Capture current time with column values:
SELECT id, name, LOCALTIME AS query_time
FROM people;
This query captures the current time of day without time zone for each row in the people table at the moment of execution.
Conclusion
The PostgreSQL LOCALTIME function is a fundamental tool for retrieving the current time of day without time zone and performing time-based calculations. Understanding how to use the LOCALTIME function and its syntax is essential for accurate time-based operations in PostgreSQL databases.