g. These. This query compares revenue per quarter for 2018. LOCALTIME(precision) Arguments. Right now the cod. Here is my solution adapted to the question given: SELECT DATE_TRUNC ('minute', NOW ()) - MAKE_INTERVAL (MINS => MOD (EXTRACT (MINUTE FROM NOW ())::INTEGER, 15)) Explanation: DATE_TRUNC the timestamp to. com PostgreSQL version: All Operating system: All Description: date_trunc('quarter',. 9. CREATE OR REPLACE FUNCTION round_time (timestamp with time zone) RETURNS timestamp with time zone AS $$ SELECT date_trunc ('hour', $ 1) + interval '5 min' * round (date_part ('minute', $ 1) / 5. I have this problem. Adding a month gives you the first of the following month. TRUNC(timestamp) Arguments. quarter: Quarter (1 to 4) second: Seconds (and fractional. 4. DATE_TRUNC (date, < Parameters. Neither of those expressions will make use of an index on created - you would need to create an expression based index with the expression used. extract関数の場合は、extract (month from request_time)という書き方だったが、date_trunc関数ではmonthをシングルクォーテーションで囲む必要がある。. Note that the 'first day of the week' is not uniform across databases. 3. Formats timestamp as a string using format. For a more comprehensive guide. SQL Server: Date truncation for custom time periods like year, quarter, month, etc. 1 Answer. These SQL-standard functions all return. appointment_date::date + appointment_end_time::time. PostgreSQL - DATE/TIME Functions and Operators. date_trunc () was added in PostgreSQL 7. The date_trunc function in redshift is specifically used to truncate the specified precision. Takes two arguments, the date to truncate and the unit of. The SELECT statement below extracts the quarter each date_renting falls in. RTRIM (‘abcxxzx’, ‘xyz’) ‘abc’. But, 'quarter' is invalid for interval. , for the Oracle database: sale_date >= TRUNC (sysdate) AND sale_date < TRUNC (sysdate + INTERVAL '1' DAY) Another common obfuscation is to compare dates as strings as shown in the following PostgreSQL example:6. Assuming data type timestamp. The DATE_TRUNC () function in Postgres truncate a date or time value to a specific precision. 3. The date_trunc function shortens timestamps so they are easier to read. These SQL-standard functions all return values based on the start. The special difficulty of your task: you want the ceiling, not the floor (which is much more common). now (). In this article I will go over the three date/time related data types, and the two most useful date/time functions…postgresql error: function date_trunc(unknown, text) does not exist LINE 1 #9783. A column of data type TIMESTAMP or an expression that implicitly evaluates to a TIMESTAMP type. Postgres’ DATE_PART and EXTRACT functions would previously evaluate to the same output. The date_trunc function contains the two input parameters, i. The Oracle code that I posted returns april 22, so I need postgres to do the same. The table currently has nearly 5 million rows and this query currently takes 8 seconds to execute. The following illustrates the. lead_id) as "# New Leads" from leads l where l. Date Part Extracted from Input Date / Timestamp. 3. - It retrieves the trimmed part with a specific precision level. The DATE_TRUNC () function is particularly useful for time series analysis to understand how a value changes over time. 1 starts: 9. select to_char (date_trunc ('month', l. PostgreSQL provides a number of different date and time functions by default that can be used to calculate these kinds of KPIs. 1 Answer. PostgreSQL provides a number of functions that return values related to the current date and time. Example 2: Truncate a TIMESTAMP value to the beginning of the hour. 2. g. #. 16. Sorted by: 3. Consequently, the timestamp will be rounded/truncated based on the specified date field. This is used in subquery cal to generate a list of all dates in your data. ). The DATE_TRUNC function is useful when. (Values of type date and time are cast automatically to timestamp or interval, respectively. Note: This shows two methods of doing the conversion, the first is the standard method. The DATE type in PostgreSQL can store a date without an associated time value: PostgreSQL uses 4 bytes to store a date value. This PostgreSQL tutorial explains how to use the PostgreSQL date_part function with syntax and examples. The date function used to truncate a date or datetime value to the start of a given unit of duration. WHERE date_survey >= date_trunc('year', now()); Or maybe add EXTRACT('quarter' FROM date_survey) AS start_season to add the quarter number. Is that what you want?Use union all:. trunc; Date/Time Functions. The general idea is to get the current day of the week, dow, subtract 7, and take the abs, which will give you the number of days till the end of the week, and add 1, to get to Monday. SELECT date_trunc ('quarter', now()); date_trunc-----2021-01-01 00:00:00+00. date_trunc¶. In PostgreSQL, DATE_TRUNC Function is used to truncate a timestamp type or interval type with specific and high level of precision. +01 +02 etc depends on your time locale's daylight saving rules. 指定した単位（month）以下の値が切り捨てられ、 年 月という結果. 9. It shows a similar result, converting the date to a month and year value, which changes the day to the first of that month. ) Details: 'quarter' is not mentioned in the doc as valid fields for date_trunc(). Table 9-23 lists them. To have one row per minute, even when there's no data, you'll want to use generate _ series. date_trunc ( field, source [, time_zone ]) source is a value expression of type timestamp, timestamp with time zone, or interval. Group by on Postgresql Date Time. The quarter of the year (1 - 4) that the date is in. 5. Delaying Execution. For instance, if you add a month to the 31st of January, with add_months,. Share. century. - Return Type: TIMESTAMP. 5. If you want both quarter and year you can use date_trunc: SELECT date_trunc('quarter', published_date) AS quarter This gives the date rounded to the. This PostgreSQL tutorial explains how to use the PostgreSQL date_part function with syntax and examples. SELECT DATE_TRUNC ('quarter', current_date ()); Copy. 9. たとえば、最も近い分、時間、日、月などに切り捨てることができます。. What I need is to "round down" the month to day one, and I. The following shows the syntax of the Oracle TRUNC() function:. RTRIM. It can also truncate the value to a specified. If there are really 250000 different days in your table, you probably cannot do much better than this. It may be ugly, but it sure works! Here is my query: SELECT Date, interval (trunc (date_part ('epoch', time)/1800) * 1800) AS HALFHOUR, SUM (Data) FROM Table GROUP BY Date, HALFHOUR; This seems to work great, and I don't see any performance hit either. Elasticsearch SQL accepts also the plural for each time unit (e. 1. 9. SELECT EXTRACT(QUARTER FROM TIMESTAMP '2001-02-16 20:38:40'); Result: 1 second. RPAD (‘ABC’, 6, ‘xo’) ‘ABCxox’. Return value. Day (number) of the month. where precision is the precision to which you want to truncate the date or time (e. It’s possible in Postgres to truncate or round a given timestamp to some given level of precision. If I want to group a column of timestamps, say registered_at by the day on which they occurred, I can use either date_trunc('day', registered_at) or registered_at::date. These SQL-standard functions all return. Interprets an INT64 expression as the number of days since 1970-01-01. start_date::timestamp, well_schedules. Extract QUARTER from Timestamp in Postgresql: Within the Extract keyword we have to mention QUARTER as we are getting quarter from timestamp. Let’s learn how the DATE_TRUNC () function work in Postgres: SELECT DATE_TRUNC ('Year', TIMESTAMP ' 2022 - 08 - 02 11: 12: 14 '); The output shows that the DATE_TRUNC () function resets all the values of the input timestamp (other than the specified date part, i. Current Date/Time. ) field selects to which precision to truncate the input value. Read: Postgresql date_trunc function Postgresql date add year. Both solutions include the last day of the previous month and also include all of "today". 2. ). The date function used to truncate a date or datetime value to the start of a given unit of duration. 9. Let’s add a year to any date. The format of the date in which it is stored and retrieved in PostgreSQL is yyyy-mm- dd. (. Sorted by: 2. pto_start_date < (date_trunc ('quarter', now () - INTERVAL '1 month') + INTERVAL. The date is complete (year, month, and day). Use the aggregate FILTER clause in Postgres 9. "GROUP BY date_trunc also? @Bravo: yes you need to repeat the expression in the group by clause. time_zone. PostgreSQL has several of functions for manipulating the dates such as extracting. . date_trunc. 使用函数截取日期的年份 要截取一个日期的年份，我们可以使用extract函数。1. Introduction to the PostgreSQL DATE_PART function. create table foo ( first_of_month date not null check (extract (day from first_of_month) = 1) ); insert into foo (first_of_month) values ('2015-01-01. EXTRACT (part FROM date) We state the type of extraction we want as part and then the source to be extracted date. table` GROUP BY ddate; LIMIT 100; and maybe withouth the LIMIT clause: SELECT ; DATE_TRUNC (date, < Parameters. Adding date_trunc('quarter', your_date) to your start date will guarantee you start with the beginning of a quarter. note: similar question as DATE lookup table (1990/01/01:2041/12/31). It's best explained by example: date_trunc('hour',TIMESTAMP '2001-02. To return. date=to_char (date_trunc ('day', se. The PostgreSQL date_part function extracts parts from a date. These SQL-standard functions all return. Dates are stored using the DATE datatype in the PostgreSQL database. Special calculation is needed for week/quarter. I've looked around and I can't figure out the right syntax for accessing the month and comparing with the current month. Share. Jun 27, 2014. Postgres Pro provides a number of functions that return values related to the current date and time. I'm making my first laravel project, using postgres, and I'd like to be able to access all the people with a birthday this month (my people table has a birthdate field that's a date). 9. Exercise care with lower. l_date is the column where I would pull the date from. Any valid year (e. , week, year, day, etc. if you want timestamp instead of timestamptz cast the date to timestamp first. Thanks, -Lars On Thu, 20 Jul 2000, Tom Lane wrote: > Lars. 1. Get the number of remaining days after excluding date ranges in a table. PostgreSQL uses 4 bytes to store a date value. We’ll use it for different. My SQL is: SELECT date_trunc('week', '2020-06-01'::timestamp)::date ||'-'|| (date_trunc('week', '2020-06-01'::timestamp)+ '6 days'::interval)::date; However, using. “Year” must be passed. amount), DATE_TRUNC('quarter', orders. SELECT EXTRACT(QUARTER FROM TIMESTAMP '2001-02-16 20:38:40'); Result: 1. 2 Answers. Share. In PostgreSQL, the DATE_TRUNC () function trims unnecessary values from the date and time and returns a result with specific precision. Learn how to round or truncate timestamps in PostgreSQL for effective time-based grouping using the date_trunc function. Oracle's DATE data type (which is what sysdate returns) always contains a time part which can not be removed. 9. These SQL-standard functions all return values based on the start time of the current. Syntax. Example 1: Truncate a DATE value to the beginning of the month. 1 20210206, 64-bit. Hey so im trying to query from a database, using Sequelize (Node. g. Example 3:. A date does not represent a specific time period; it can differ based on timezones. For formatting functions, refer to Section 9. DATETIME_TRUNC(datetime_expression, part) Example: DATETIME_TRUNC('2019-04-01 11:55:00', HOUR) Output: 2019-04-01 11:00:00. the Use of the DATE_TRUNC() Function in PostgreSQL. quarter; year; decade; century; millennium; source. But there is also no point in casting date literals to date as input parameter. date_trunc can be really helpful if you want to roll up time fields and count by day or month. DATE_FROM_UNIX_DATE. 参数 field. orafce should be among them. Delaying Execution. DATE_TRUNC returns a date or timestamp, while DATE_PART returns a subfield from a date or timestamp. To get week start and end date (as 0 for Monday and 4 for Friday): select cast (date_trunc ('week', current_date) as date) + 0 || '-->' || cast (date_trunc ('week', current_date) as date) + 4; 2015-08-17-->2015-08-21. 9. Postgres Pro provides a number of functions that return values related to the current date and time. 9. The quarter of the year (1–4) that the date is in SELECT EXTRACT(QUARTER FROM TIMESTAMP '2001-02-16 20:38:40'); Result: 1. DROP TABLE if exists d_date; CREATE TABLE d_date. I am converting a postgres app to an Oracle app. The following query SELECT the_date FROM date_trunc('day', timestamp with time zone '2001-01-1 00:00:00+0100') as the_date results to the_date 2000-12-31 00:00 Is there a way to tell . SELECT cast (created_at as date) as created_at, count (created_at) FROM forms group by 1 ORDER BY created_at asc; If you want the date in a particular time zone, date_trunc with that time zone then cast to a date. Current Date/Time. ). SELECT id, name, date_trunc('quarter', date) AS date, AVG(rank) AS rank, AVG(score) as score, country, device FROM player_daily_score GROUP BY id, name, 3, country, device ORDER BY 3 desc; If you want both quarter and year you can use date_trunc: SELECT date_trunc('quarter', published_date) AS quarter This gives the date rounded to the start of the quarter, e. The LOCALTIME function takes one optional argument:. Table 9. DATE '2000-01-02'. fujitsu. , week, month, and year. When storing a date value, PostgreSQL uses the yyyy-mm-dd format e. sql. for example 2018-10-15 will be 2018-10-01 and 2018-10-30 also will be 2018-10-01. This query, for example, works, but as soon as I try a left join with a different table there is a problem: select date_trunc ('month',created_at)::date as date , id as id from promo_code_uses order by date DESC; sounds like created_at is a standard field in many of your tables. 'QUARTER': truncate to the first date of the quarter. The following example shows how to use the date_trunc () function to truncate a timestamp value to hour part, as follows: SELECT date_trunc('hour', TIMESTAMP '2022-05-16 12:41:13. If you need to, you can have your own in the following ways as a. (In our example, we used month precision. ) as we did for the EXTRACT code. 1 starts: 9. In the docs I could only find a way to create a date from a string, e. INTERVAL allows either YEAR and MONTH to be mixed together or DAY, HOUR, MINUTE and SECOND. Connect and share knowledge within a single location that is structured and easy to search. Args:. Nice. 9. Table 9. e. date_trunc will truncate a date or timestamp to the specified date/time part. First, we have the date part specifier (in our example, 'month'). For more information, see TRUNC function. 次のように実例を示すとわかりやすいです。. 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. 0) $$ LANGUAGE SQL; Generally rounding up to. Explore options like 'second', 'minute', 'hour', 'day', or 'month' to tailor your data analysis. Previous: DATE_TRUNC function Next:. SELECT EXTRACT(quarter FROM '2015-01-01'::timestamp) - 1; Result : 0 The most frequently used Postgres date functions and business scenarios where they come in handy: Rounding off timestamps with DATE_TRUNC function. Hey so im trying to query from a database, using Sequelize (Node. 9. The GROUP BY clause in Postgres allows us to group the table’s data based on specific column(s), making it easy to analyze and understand relationships and patterns within your data. g. 2. ). (Values of type date and time. The lowest and highest values of the DATE data type are 4713 BC and 5874897 AD. I am trying to pull entries which happen after April 1st, 2019. trunc (teste TIMESTAMP WITHOUT TIME ZONE). 9999999 which your desired condition would not include). timestamp '2001-09-29 03:00' - timestamp '2001-09-27 12:00'. Extracting year from a timestamp: SELECT EXTRACT(YEAR. Note that the specifier is a string and needs to be enclosed in quotes. Finally, it returns the truncated part with a specific precision level. Here is how you can convert an epoch value back to a time stamp: SELECT TIMESTAMP WITH TIME ZONE 'epoch' + 982384720 * INTERVAL '1 second'; hour. 必需的。 它是一个字符串表示要截取到部分。您可以是使用以下值： microseconds; milliseconds; second; minute; hourBasically this expression gives you the last day of the current quarter (provided that you remove the last closing parenthese, which otherwise is a syntax error). Same as YEAROFWEEK, except uses ISO semantics. 9. How about truncating to the beginning of this month, jumping forward one month, then back one day? =# select (date_trunc ('month', now ()) + interval '1 month - 1 day')::date; date ------------ 2015-07-31 (1 row) Change now () to your date variable, which must be a timestamp, per the docs. 789'); date_trunc 2020-04-01 00:00:00date_trunc('hour', timestamp '2001-02-16 20:38:40') 2001-02-16 20:00:00: extract. Take two easy steps to create date_trunc: Break down the datetime into small parts (Year, Month, Day/Hour, Minute, Second) and extract the parts you need. I have a table where date | interval juin 1, 2022, 12:00 AM | 0 years 0 mons 0 days 0 hours 1 mins 58. year. id, generate_series(well_schedules. region, q1. Subtracts a specified time interval from a DATE value. To group data by year, you can use the DATE_TRUNC function with ‘year’ as the first argument. SELECT date_trunc('week', date::date) AS "weekly", COUNT(DISTINCT(date)) AS "working_days" FROM "public". For example, decade 201 spans from 2000-01-01 to. 33 shows the available functions for date/time value processing, with details appearing in the following subsections. If the contraint should apply to the tservice as type "date" you might as well create the tservice column as type "date" instead. All hours in a day: SELECT TRUNC (SYSDATE) + (LEVEL - 1) / 24 FROM DUAL CONNECT BY LEVEL <= 24. (. You are correct, I meant quarter, but typed month. SELECT DATE_TRUNC('quarter', TIMESTAMP '20200430 04:05:06. AT TIME ZONE. 9. date_trunc ('month',current_date) + interval '1 month' - interval '1 day'. The following example extracts the century from a time stamp: SELECT date_part('century', TIMESTAMP '2017-01-01'); date_part -----21 (1 row) Code language: SQL (Structured Query Language) (sql) Into something like: SELECT COUNT (*) = 1 INTO v_exists FROM pg_tables WHERE schemaname = 'public' AND tablename = v_partition_name and v_date_from < date_trunc ('year', current_date); This will return 1 only in the case when partition is from previous year. So first the timestamp is converted to a date (that does not have a time), and then the time value is added to that, which yields a timestamp. 6. 9. 9. . The DATE_PART () function extracts a subfield from a date or time value. 8. The syntax of the function is as follows: DATE_TRUNC ('precision', expression); where expression is a timestamp or an interval to truncate. Teams. 3. You can then add more conditions to the CASE/WHEN for additional quarters. This query is working for me to give me the running total of total IDs by week. The time zone. The DATE_PART() function extracts a subfield from a date or time value. 9. One way to do this is to "truncate" the date to the start of the month, then add 8 days: vardate := date_trunc ('month', vardate)::date + 8; date_trunc returns a timestamp that's why the cast ::date is needed. EXTRACT (field FROM source) The extract function retrieves subfields such as year or hour from date/time values. A bigint is not "a timestamp", so you must convert the number to a date before you can apply date_trunc () on it: Select date_trunc ('day', to_timestamp (rp. first day of year + current week * 7 days = closest preceding date with same day of week as the first day of the year. PostgreSQL Date Functions Manipulation. RPAD (‘ABC’, 6, ‘xo’) ‘ABCxox’. day::date FROM generate_series (timestamp '2004-03-07' , timestamp '2004-08-16' , interval '1 day') AS t (day); Additional date_trunc () is not needed. The function date_trunc is conceptually similar to the trunc function for numbers. SELECT DATE_TRUNC('month', TIMESTAMP '2005-05-21 15:30:30'); Result: 2005-05-01 00;00:00 The basic syntax of the DATE_TRUNC function is as shown below: DATE_TRUNC(precision, source); where precision is the precision to which you want to truncate the date or time (e. Format date with to_char; Setup. g. The following are valid field names. Select date_trunc ('week',dateTime) Date_week, Max (Ranking) Runing_Total_ID from (select datetime, id , dense_rank () over (order by datetime) as Ranking from Table1) group by 1. You can also use add_months to subtract months by specifying a negative integer. For a date column: SELECT * FROM tbl WHERE my_date BETWEEN date_trunc('month', now())::date - 1 AND now()::date You can subtract plain integer values from a date (but not from a timestamp) to subtract days. date_trunc. ·. , hour, week, or month and returns the truncated timestamp or interval with a level of precision. Use the below aggregate function with date_trunc and to_char function to use group by day in PostgreSQL. The Oracle TRUNC() function returns a DATE value truncated to a specified unit. Table 9. 9. Sorted by: 2. Here is how I make a standard quarterly score average with default quarter. 1 year and 2 months. timestamp)) from rollup_days as rp; To convert the timestamp back to a bigint, use extract ()Use the date_trunc method to truncate off the day (or whatever else you want, e. In this article, we will see how we can store,. I found these two procedures that abstract equivalent logic: CREATE OR REPLACE FUNCTION first_of_week(date) returns date AS $$ SELECT ($1::date-(extract('dow' FROM $1::date)*interval '1 day'))::date; $$ LANGUAGE SQL STABLE STRICT; CREATE OR. I need it to return april 22. I have a slow query that generates a report of account activity per week over the past year. The DATE type in PostgreSQL can store a date without an associated time value: PostgreSQL uses 4 bytes to store a date value. SELECT TRUNC(datevalue, 'MONTH') FROM datelist; Result: 01/MAR/22. Postgres quarter function. Some common precisions are year, month, week, day, hour or minute. (Values of type date and time are cast automatically to timestamp or interval, respectively. The following bug has been logged online: Bug reference: 2664 Logged by: Yoshihisa Nakano Email address: nakano. I would suggest not thinking too hard about the problem and just using the first date/time of the month. 1. The date_trunc function in redshift is specifically used to truncate the specified precision. PostGreSQL : date_trunc() returns timestamp with timezone when used on date. g. Syntax. 1 min read. , ‘year’, ‘quarter’, ‘month’, ‘day’, ‘hour’, ‘minute’, ‘second’, etc. Postgres has date_trunc which operates on timestamp or interval, and:. 1. SELECT CODE, to_char (DATE, 'YYYY-MM'), count (CODE) FROM employee where group by CODE, to_char (DATE, 'YYYY-MM') Depending on whether you want the result as text or a date, you can also write it like this: SELECT CODE, date_trunc ('month', DATE), COUNT (*) FROM employee GROUP BY CODE, date_trunc ('month', DATE); Which in your. If I use the below query, I get the result as 0. 9. "W" = week of month (1-5) (the first week starts on the first day of the month) So if the month starts on Friday, the next Thursday will still be week 1, and the next Friday will be the first day of week 2. PostgreSQL DATE_PART () function is mainly used to return the part of the date and time; the date_part function in PostgreSQL will subtract the subfield from the date and time value. - It accepts a “datePart” and a “field” as arguments. Use the function date_trunc() instead, that will be faster overall. It's much better to materialize separate columns for the year, quarter and year-quarter from the_date column, as is suggested in one of the comments. Adds a specified time interval to a DATE value. If you prefer to write standard SQL, stick to extract(). EXTRACT, date_part EXTRACT(field FROM source) The extract function retrieves subfields such as year or hour from date/time values. Add a comment. You can truncate the current date to its quarter, then remove 1 day from that (and potentially cast back to date): -- You really only need the last column, the other two just show the different steps in the process SELECT DATE_TRUNC ('quarter', CURRENT_DATE) , DATE_TRUNC ('quarter',. 19, earlier I have made the following Query. This function truncates a date/time value to a specified precision. 9. Stack Overflow. 9. The DATE_PART() function returns a value whose type is double precision. select date_trunc ('minute', created_at), -- or hour, day, week, month, year count(1) from users group by 1. created), 'YYYY-MM-DD')) GROUP BY d. , week, year, day, etc. Note that the specifier is a string and needs to be enclosed in quotes. One truncates a date to the precision specified (kind of like rounding, in a way) and the other just returns a particular part of a datetime. You. 8. When storing a date value, PostgreSQL uses the yyyy-mm-dd format e. The date_trunc function truncates a TIMESTAMP or an INTERVAL value based on a specified date part e. Date: 20 July 2000, 05:00:19. 1. Table 9-27 illustrates the behaviors of the basic arithmetic operators ( +, *, etc. The PostgreSQL formatting functions provide a powerful set of tools for converting various data types (date/time, integer, floating point, numeric) to formatted strings and for converting from formatted strings to specific data types. AT TIME ZONE. This uses PostgreSQL’s date_trunc () function, along with some date arithmetic to return the results we want. date_trunc('month', current_timestamp) gives you the start of "this month" so in March this would be 2021-03-1 as the comparison for the upper limit is done using < it will include everything on the last day of February (including 23:59:59. extract() complies with the SQL standard, date_part() is a Postgres specific query. The DATE_TRUNC () function in Postgres truncate a date or time value to a specific precision. 9. -- date_trunc（日付の切り捨て）の構文 date_trunc( 精度 , 日付・時刻 ); 精度には'year'、'month'、'day'等を指定します。. Realizing this is an old answer, but I recently ran into this. PostGreSQL : date_trunc() returns timestamp with timezone when used on date. yosihisa@jp. 'quarter' is valid for date_trunc() and extract() SELECT date_trunc ('quarter', now()); date_trunc-----2021-01-01 00:00:00+00 The DATE_PART () function extracts a subfield from a date or time value. This is where PostgreSQL can help us with some date functions. 2. The EXTRACT() function returns a double precision value. But there is also no point in casting date literals to date as input parameter. . "deleted_at" IS NULL). source is a value expression of type timestamp or interval.