![]() In this tutorial, you have learned how to use the PostgreSQL date_trunc function to truncate a timestamp or an interval value. The following shows the output: staff_id | y | rental Staff_id Code language: SQL (Structured Query Language) ( sql ) Similarly, you can count the number of rentals by staff per year as follows: SELECT I have strange behaviour of COALESCE function of PostgreSQL. The COUNT function counts the number of rentals and the GROUP BY clause groups the rentals by month. I think I can replace somefunc with COALESCE in my example, and by ordering the timestamp fields the way I need, it will return the first non-null timestamp. In this query, the date_trunc function truncates the rental date to month part. Oooh, COALESCE gets me most of the way there. You can count the number of rentals by month by using the date_trunc function as follows: SELECT Make it a view or a subselect to join it onto your table via id, then coalesce as you intended. See the following rental table in the sample database: I have no PostgreSQL access to validate, but something like this should work: Make a query containing the dates to set to: SELECT id, costdate FROM tblName WHERE cost is not null. ![]() The function returns a TIMESTAMP whose precision level is minute: date_trunc If you want to truncate a TIMESTAMP value to a minute, you pass the 'minute' string as the first argument: SELECT date_trunc( 'minute', TIMESTAMP ' 02:09:30') Instead, you should be using totimestamp(), which can parse a string and return a timestamp. The following example truncates a TIMESTAMP value to hour date part: SELECT DATETRUNC('hour', TIMESTAMP ' 02:09:30') Code language: SQL (Structured Query Language. The datetrunc function returns a TIMESTAMP or an INTERVAL value. The output of tochar is a string, and the way you are using it would cause Postgres to reject it. It could be an expression that evaluates to a timestamp or an interval. The date_trunc function returns a result with the hour precision. Another problem you have is that you are incorrectly using tochar to format your timestamp data. ![]() The following example truncates a TIMESTAMP value to hour date part: SELECT DATE_TRUNC( 'hour', TIMESTAMP ' 02:09:30') The date_trunc function returns a TIMESTAMP or an INTERVAL value. It could be an expression that evaluates to a timestamp or an interval. The field argument is a TIMESTAMP or an INTERVAL value to truncate. The datepart argument is the level of precision used to truncate the field, which can be one of the following: The following illustrates the syntax of the date_trunc function: date_trunc('datepart', field)Ĭode language: SQL (Structured Query Language) ( sql ) How to COALESCE a timestamp column postgresql timestamp postgresql-9. The date_trunc function truncates a TIMESTAMP or an INTERVAL value based on a specified date part e.g., hour, week, or month and returns the truncated timestamp or interval with a level of precision. Introduction to the PostgreSQL date_trunc function Summary: this tutorial shows you how to use the PostgreSQL date_trunc() function to truncate a timestamp or interval to a specified level of precision.
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