, ‘year’, ‘quarter’, ‘month’, ‘day’, ‘hour’, ‘minute’, ‘second’, etc. source is a value expression of type timestamp or interval. If the contraint should apply to the tservice as type "date" you might as well create the tservice column as type "date" instead. Thank you so much! Keep safe everyone. The EXTRACT() function returns a double precision value. This query compares revenue per quarter for 2018. 3. This PostgreSQL tutorial explains how to use the PostgreSQL date_part function with syntax and examples. DATE_TRUNC returns a date or timestamp, while DATE_PART returns a subfield from a date or timestamp. On 29/10/2018 16:26, Andreas Karlsson wrote: > On 10/29/2018 04:18 PM, Vik Fearing wrote: >> A use case that I see quite a lot of is needing to do reports and other >> calculations on data per day/hour/etc but in the user's time zone. But there is also no point in casting date literals to date as input parameter. source is a value expression of type timestamp or interval. The date_part function is modeled on the traditional Ingres equivalent to the SQL -function extract: The precision values are a subset of the field identifiers that can be used with the EXTRACT() and DATE_PART() functions. Postgres has lots of functions for interval and overlap so you can look at data that intersects. date_trunc is only defined for timestamp with time zone and timestamp inputs. 9. Note that the latter. to_char and all of the formatting functions let you query time however you want. These. 32 shows the available functions for date/time value processing, with details appearing in the following subsections. -- 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。. These SQL-standard functions all return values based on the start time of the current. Add a comment. The DATE_TRUNC () function is particularly useful for time series analysis to understand how a value changes over time. Ex:If I have 2010-01-01, I would like to return 2010-03-31, and so on. millenium. g. DATE_FROM_UNIX_DATE. transaction_date) but the count (distinct) will do a sort so it will take you a lot of time. lead_id) as "# New Leads" from leads l where l. PostgreSQL provides a number of different date and time functions by default that can be used to calculate these kinds of KPIs. source must be a value expression of type timestamp, time, or interval. , “Year” in the above example) to their initials. timestamp '2001-09-29 03:00' - timestamp '2001-09-27 12:00'. The function date_trunc is conceptually similar to the trunc function for numbers. You. Stack Overflow. In the above output, it shows the output like a day of the timestamp value but we can find the. This converts the date column my_date to date (cuts the time part) and if you cast it back into timestamp it gets the 0 time. The date_trunc function in redshift is specifically used to truncate the specified precision. Here’s a bit of code adapted from the PostgreSQL wiki that I like for creating the ever necessary date dimension in PostgreSQL. 1994-10-27. You can't cast tservice when creating the constraint. Recently, I have been getting familiar with PostgreSQL(using 8. 9. SELECT EXTRACT(QUARTER FROM TIMESTAMP '2001-02-16 20:38:40'); Result: 1. currently I am coding the exact date for the last quarter, the quarter before and the quarter one year ago. CREATE TABLE dim_date ( dim_date_id INT NOT NULL, date_actual DATE NOT NULL, epoch BIGINT NOT NULL, day_suffix VARCHAR(4) NOT NULL, day_name VARCHAR(9) NOT NULL, day_name_tr VARCHAR(9) NOT NULL,. You can fix a date or remove days from current day. 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。. Date_selector >) AS ddate, SUM (value1) AS value1FROM `project. 9. ) Example of grouping sales from orders by month: select SUM(amount) as sales, date_trunc('month', created_at) as date from orders group by. DATE_DIFF. Try to envision time periods on a straight time line and move them around before your eyes and you will see the necessary conditions. 9. In order to group our orders by month, in PostgreSQL we'll use the date_trunc built-in function. ) field selects to which precision to truncate the input value. age; current_date; current_time; current_timestamp; date_part; extract; localtime;. The quarter of the year (1 - 4) that the date is in. 9. ). It’s possible in Postgres to truncate or round a given timestamp to some given level of precision. but otherwise behaves similarly to DATE_TRUNC CASE TRIM(TRAILING 's' FROM LOWER( $1 -- in_unit )) WHEN 'microsecond' THEN 0. The following table lists the behaviors of the basic arithmetic operators −. I have a table where date | interval juin 1, 2022, 12:00 AM | 0 years 0 mons 0 days 0 hours 1 mins 58. Truncates a DATE, TIME, or TIMESTAMP to the specified precision. 2) at or above day precision, the time zone offset is recalculated, according to the current TimeZone configuration. For example, TRUNC (TO_DATE ('2013-08-05'), 'QUARTER') returns the first date in the third quarter of the year 2013, which is July 1, 2013. Q&A for work. g. Some details are different for date or timestamptz. PostgreSQL uses 4 bytes to store a date value. Its type is timestamp without time zone. ). It's best explained by example: date_trunc('hour',TIMESTAMP '2001-02. Delaying Execution. , hour, week, or month and returns the truncated. Date_selector >) AS ddate, SUM (value1) AS value1FROM `project. dim_time__month_start_date date NOT NULL, dim_time__week_start_date date NOT NULL, dim_time__quarter_start_date date NOT NULL, dim_time__year_start_date date NOT NULL, The redundant columns wouldn't even help performance of the query at hand. Ordering by month & year numbers in Postgres. 1. In certain cases, it can also speed up some of your queries. The resulting interval is can the be added to the desired date to give the desired date with the prior time. Use the aggregate FILTER clause in Postgres 9. 2k 3 64 88. g. Date: 20 July 2000, 05:00:19. --set the first day of the. SELECT TRUNC(datevalue, 'MONTH') FROM datelist; Result: 01/MAR/22. 4 or later. 2) and found the date_trunc function extremely useful for easily matching time stamps between certain days/months/etc. 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. Table 9-28 shows the available functions for date/time value processing, with details appearing in the following subsections. GitHub Gist: instantly share code, notes, and snippets. EXTRACT (part FROM date) We state the type of extraction we want as part and then the source to be extracted date. TRUNC(timestamp) Arguments. AT TIME ZONE. create table test (start date ,"end" date); insert into test values ('2019-05-05','2019-05-10') , ('2019-05-25','2019-06-10') , ('2019-07-05','2019-07-10') ; I am looking for the following output, where for every date between the start and end the person is available only. So using date_trunc ('week',now ())-'1 s'::interval; on the right side of your date operator should work. Follow. Postgres Pro provides a number of functions that return values related to the current date and time. The following are valid field names. These SQL-standard functions all return values based on the start time of the current transaction:What you should do: Order by year and month. This example uses TRUNC on a date to truncate it to a day. date_trunc('hour', interval '2 days 3 hours 40 minutes') 2 days 03:00:00:. 000001 WHEN 'millisecond' THEN 0. These SQL-standard functions all return values based on the start time of the current transaction:DATE_TRUNC. We had discussed about the Date/Time data types in the chapter Data Types. Postgres has lots of functions for interval and overlap so you can look at data that intersects. That is easy enough to add. The quarter of the year (1 - 4) that the day is in. The PostgreSQL LOCALTIME function returns the current time at which the current transaction starts. quarter. 'QUARTER': truncate to the first date of the quarter. So using date_trunc ('week',now ())-'1 s'::interval; on the right side of your date operator should work. Finally, it returns the truncated part with a specific precision level. PostgreSQL has several of functions for manipulating the dates such as extracting. table` GROUP BY ddateTruncates a TIMESTAMP and returns a DATE. 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. Checkout DoctrineExtensions. WEEK: The number of the week of the year that the day is in. EXTRACT, date_part EXTRACT(field FROM source) The extract function retrieves subfields such as year or hour from date/time values. In PostgreSQL, DATE_TRUNC Function is used to truncate a timestamp type or interval type with specific and high level of precision. Data warehouse support for the EXTRACT function Google BigQuery, Amazon Redshift, Snowflake, Postgres, and Databricks all support. date_trunc () The return type of the date_trunc function is a timestamp. Sorted by: 3. 4. 2. All hours in a day: SELECT TRUNC (SYSDATE) + (LEVEL - 1) / 24 FROM DUAL CONNECT BY LEVEL <= 24. In Postgres, you can use the EXTRACT(), DATE_TRUNC(), and DATE_PART() function to extract the month from a date field and then use the GROUP. The date function used to truncate a date or datetime value to the start of a given unit of duration. The DATE_PART() function returns a value whose type is double precision. answered Dec 28, 2011 at 13:33. Section 9. To store date values, you use the PostgreSQL DATE data type. table` GROUP BY ddate; LIMIT 100; and maybe withouth the LIMIT clause: SELECT ; DATE_TRUNC (date, < Parameters. source must be a value expression of type timestamp, time, or. select cast (date_trunc ('month', current_date) as date) 2013-08-01. g. Syntax. 9. 9. 436'); Sample Output:. To generate a series of dates this is the optimal way: SELECT t. Interprets an INT64 expression as the number of days since 1970-01-01. In Postgresql, to truncate or extract the week of the timestamp value, pass the week as a string to the date_trunc function. The following bug has been logged online: Bug reference: 2664 Logged by: Yoshihisa Nakano Email address: nakano. The cast to date ( day::date) does that implicitly. Table 9. You can't cast tservice when creating the constraint. pyspark. 2. Date/Time Functions and Operators. character (the_year)) before you can concatenate it. The following shows the syntax of the Oracle TRUNC() function:. Thank you very much for your. It puts that value in. 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. This is utterly confusing and annoying. Isolating hour-of-day and day-of-week with EXTRACT function. 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. 0) $$ LANGUAGE sql; Pad on the right of a string with a character to a certain length. 9. 24')); Result: 2017-02-14 20:00:00. DATE_TRUNC returns a date or timestamp, while DATE_PART returns a subfield from a date or timestamp. yosihisa@jp. In PostgreSQL, various inbuilt functions like DATE_PART(), EXTRACT(), and DATE_TRUNC() are used with the GROUP BY clause to group the table’s data by a specific date field. toLocalDateTime () When you use date_trunc ('day', now () at time zone 'Asia/Tehran') (column tehran_local_start_of_today) it indicates the start of today in Tehran local. The quarter of the year (1–4) that the date is in. Date_trunc. Definition of PostgreSQL Trunc () PostgreSQL’s trunc () function is used to truncate the decimal places to a certain precision. 2017-05-14 20:38:40. Gets the number of intervals between two DATE values. The first day of a week (for format element 'week') is defined by the parameter NLS_FIRST_DAY_OF_WEEK (also see ALTER SESSION and ALTER SYSTEM ). date_trunc can be really helpful if you want to roll up time fields and count by day or month. You are correct, I meant quarter, but typed month. I have the blow query that I'm trying to use in a BI tool. Now, let us see the Date/Time operators and Functions. 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. date_dim_id INT NOT NULL, date_actual DATE NOT NULL, epoch BIGINT NOT NULL, day_suffix VARCHAR(4) NOT NULL, day_name. Read: Postgresql date_trunc function Postgresql date add year. date_trunc. Table 9. demo:db<>fiddle. created), 'YYYY-MM-DD')) GROUP BY d. These queries work fine in oracle but am in the process of converting it to a postgres query but it complains. Exercise care with lower. SELECT date_trunc. PostgreSQL provides a number of functions that return values related to the current date and time. (Expressions of type date are cast to timestamp and can therefore be used as well. How to truncate date in PostgreSQL? Ask Question Asked 10 years, 2 months ago Modified 10 years, 2 months ago Viewed 42k times 22 I'm trying to select all transactions in PostgreSQL 9 that happened earlier than the end of the last week. dataset. Any valid year (e. Truncates a DATE value. 2-1) on x86_64-pc-linux-gnu, compiled by gcc (Ubuntu 10. These SQL-standard. It is only meant as a quick reference to those I use most often. Also, you need to study the week in snowflake. Hey so im trying to query from a database, using Sequelize (Node. 31 illustrates the behaviors of the basic arithmetic operators ( +, *, etc. RTRIM. Add a comment. You need to remove the concat () as it turns the timstamp into a varchar. config. GROUP BY date_trunc('day', datelocal) ORDER BY date_trunc('day', datelocal); A bit more noisy code, but faster (and possibly easier to optimize for the query planner, too). source must be a value expression of type timestamp, time, or interval. I am just highlighting the date modification part) ## 6 days interval "date_trunc ('month', created_at) + (date_part ('day', created_at)::int - 1) / 6 * interval '6 day'" ## 10 min interval "date_trunc ('hour', created_at) + date_part ('minute', created_at)::int / 10 * interval '10 min'". test=# CREATE STATISTICS mystats ON (date_trunc('day', t)) FROM t_timeseries ; CREATE STATISTICS test=# ANALYZE ; ANALYZE What you’ve just told the system is to create a sample for date_trunc(‘day’, t) and maintain this information just like simple column-related statistics. The Oracle code that I posted returns april 22, so I need postgres to do the same. In the following example, DATE_TRUNC retrieves the beginning of the current month, adds one month to retrieve the beginning of the next month, and then subtracts 1 day to determine the last day of the current month. INTERVAL '1-2' YEAR TO MONTH. “Year” must be passed. I have a date field in a postgresql database (field name is input) how can I extract the month only from the date field? I used the syntax below, but I want it to show the actual month name, not a numeric value for the month. That will give us an integer that's a multiple of 7. 9. It's bad practice but you might be forgiven if you use. try this : SELECT datepart (quarter,transaction_date), count (distinct UNIQUE_ID) as cnt FROM panel WHERE (some criteria = 'x') GROUP BY datepart (quarter,p. Thanks, -Lars On Thu, 20 Jul 2000, Tom Lane wrote: > Lars. Optional. Here’s an example that returns the last day of the current month: SELECT (date_trunc ('month', now ()) + interval '1 month - 1 day'); Result: 2022-04-30 00:00:00+10. This query is working for me to give me the running total of total IDs by week. , hour, week, or month and returns the truncated timestamp or interval with a level of precision. Basically, there are two parameters we. js ORM for postgreSQL), im trying to group by date range, and keep a count of how many items where in that table. To have one row per minute, even when there's no data, you'll want to use generate _ series. By implementing the feature above, we are going to learn the following date functions in PostgreSQL: Truncate date with date_trunc; Extract date parts, such as weekday, month and year with date_part. md","contentType":"file"},{"name":"Script-CREATE-TABLE-dim_date. Right now the cod. date_trunc函数根据指定的日期部分（例如小时、周或月）截断一个TIMESTAMP或一个INTERVAL值，并以一定精度返回截断的时间戳或间隔值。[email protected]_trunc ('month',current_date) + interval '1 month' - interval '1 day'. 662522'); date_trunc --------------------- 2022-05-16 12:00:00. Syntax. Table 9. Use the DATE_TRUNC() function if you want to retrieve a date or time with a specific precision from a PostgreSQL database. performance. The DATE type in PostgreSQL can store a date without an associated time value: PostgreSQL uses 4 bytes to store a date value. appointment_date::date + appointment_end_time::time. The PostgreSQL date_part function extracts parts from a date. So if the date in the field input was 04/26/2016 this syntax returns 4,. RTRIM (‘abcxxzx’, ‘xyz’) ‘abc’. The DATE_TRUNC () function is used to truncate a date, time, or timestamp to a specified interval, such as the day, week, or month, in PostgreSQL and SQL. However, date_trunc('day', created) is not equivalent to the other expressions, because it returns a timestamp value, not a date. You may try subtracting 3 months from the input date, and then check whether the resulting date fall within the first or second half of the year: SELECT CASE WHEN EXTRACT (month FROM input_date) - INTERVAL '3 MONTH' BETWEEN 1 AND 6 THEN 1 ELSE 2 END AS fiscal_half FROM yourTable; The trick. Notes. example: SELECT date_trunc ('hour', time 'columnName') from tableName. I have an sql query am trying to make to my postgres db. dim_time__month_start_date date NOT NULL, dim_time__week_start_date date NOT NULL, dim_time__quarter_start_date date NOT NULL, dim_time__year_start_date date NOT NULL, The redundant columns wouldn't even help performance of the query at hand. Here's the best GROUP BY query I have so far: SELECT d. answered Aug 18, 2015 at 10:52. Date/Time Functions. 30 shows the available functions for date/time value processing, with details appearing in the following subsections. 12,516 ExpertMod8TB. column. 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 . A date literal in SQL syntax is formatted as follows. time_zone. 3. Possible Values. Table 9. When used to aggregate data, it allows you to find time-based trends like daily purchases or messages per second. 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. date_trunc () is a system function for truncating a timestamp or interval to a specified unit. The DATE type in PostgreSQL can store a date without an associated time value: PostgreSQL uses 4 bytes to store a date value. Adds a specified time interval to a DATE value. Current Date/Time. source is a value expression of type timestamp or interval. Sintaksis. To represent an absolute point in time, use a timestamp instead. Here, I’ll try to show you how existing production PostgreSQL tables can be partitioned, while also presenting you with a few options and their trade-offs. As one gets converted to the other, there is absolutely no performance difference. , ‘year’, ‘quarter’, ‘month’, ‘day’, ‘hour’, ‘minute’, ‘second’, etc. ) field is an identifier or string that selects what field to. 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. Syntax: add_months(date, integer). the Use of the DATE_TRUNC () Function in PostgreSQL. Users coming from Oracle will recognize this one. 9. SELECT date_trunc('week', date::date) AS "weekly", COUNT(DISTINCT(date)) AS "working_days" FROM "public". 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',. For formatting functions, refer to Section 9. 9. It takes 4 bytes of memory to store any date value in PostgreSQL. sales FROM Q2; Or, you could dispense with the CTEs and just use OR:. SELECT EXTRACT(QUARTER FROM TIMESTAMP '2001-02-16 20:38:40'); Result: 1 second. Teams. Also, I'm leaving out '10:00'. For example, if we want to truncate the date and time value to the nearest hour or week, it is possible to truncate using the date_trunc function. These SQL-standard functions all return values. The following illustrates the. ) field selects to which precision to truncate the input value. sql. Takes two arguments, the date to truncate and the unit of. This can be generalized to any type of grouping. 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. create table. you need to qualify the field with the table name. Group by on Postgresql Date Time. ·. Introduction to the PostgreSQL DATE_PART function. This is the query: select to_char (calldate,'Day') as Day, date_trunc (calldate) as transdate, Onnet' as destination,ceil (sum (callduration::integer/60. EXTRACT, date_part EXTRACT (field FROM source) The extract function retrieves subfields such as year or hour from date/time values. 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. SELECT date_trunc($1, purchase_date) unit_of_time, SUM(total) FROM orders WHERE purchase_date >= $2 AND purchase_date <= $3 GROUP BY unit_of_time ORDER BY unit_time; [interval, startDate, endDate] The above query works correctly for when I pass in either 'month' or 'day' as the interval variable, but gives incorrect values. The easiest thing to do is to pass in dates for the start and end of the month: select * from generate_series ( '2018-08-01' ::timestamptz, '2018-08-31' ::timestamptz, '1 day' ); That works as expected, but it's cumbersome. with ats (old_tz) as (select now() ) select old_tz, '2015-12-31'::timestamptz + (old_tz - date_trunc('day', old_tz)) new_tz from ats; OOPS. order_date) AS interval FROM orders WHERE orders. It will return the date truncated to month precision, e. g. But the start day is coming as Monday. This is utterly confusing and annoying. Table 9. e. Share. PostgreSQL DATE_PART examples. decade. 9. The problem with the selected solution is that make the month configurable so that the quarter can start at any month is not possible; you have to change the query to change the starting month. 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. The time zone. (. The first removes the hours and smaller units from the timestamp, but still returns a timestamp, while the latter returns the timestamp cast to a date. 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 . TRUNC(timestamp) Arguments. PostgreSQL's date_trunc in mySQL Ask Question Asked 12 years, 7 months ago Modified 10 months ago Viewed 43k times 26 Recently, I have been getting familiar. The following bug has been logged online: Bug reference: 2664 Logged by: Yoshihisa Nakano Email address: nakano. 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. Overall, it’s a great function to use to help you aggregate your data into specific date parts while keeping a date format. For formatting functions, refer to Section 9. 9. Adding date_trunc('quarter', your_date) to your start date will guarantee you start with the beginning of a quarter. year. All the same can be achieved by using something such as date_trunc('week', date_time) AS date_period, to summarize by weeks instead of days, instead of the definition I used. 9. 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. Only accepted if source is of timestamptz type. first day of year + current week * 7 days = closest preceding date with same day of week as the first day of the year. For formatting functions, refer to Section 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. 4. 2 Answers. The quarter of the year (1–4) that the date is in. PostgreSQL Date Functions (and 7 Ways to Use Them in Business Analysis). Here's an example: SELECT round (date_trunc ( 'day', your_date_column):: date) AS rounded_date FROM your_table; In this example, replace your_date_column with the actual name of the column that contains the date you want to round, and your_table with the name of the table where the column resides. Here’s the current timestamp. How to write the query to get the first and last date of a January and other month's in postgresql 1 Get the timestamp of the last and first day of a month in postgresSQLIn order to ignore seconds, you can use date_trunc () function. 0) $$. Alternative option. Here are some of my staple date functions. ) as we did for the EXTRACT code. SELECT date_trunc('year', TIMESTAMP '2022-05-16 12:41:13. 5. A general solution for any time interval can be based on the epoch value and integer division to truncate. 26 lists them. ). I have been trying to simulate the following Oracle statement in PostgreSQL: To reach this, I was already able to simulate the TRUNC () function receiving only one time datatype parameter, which is timestamp without time zone. com PostgreSQL version: All Operating system: All Description: date_trunc('quarter',. dayofweek_iso 部分は、 ISO-8601データ要素と交換形式の標準に従います。 この関数は、曜日を1-7の範囲の整数値として返します。1は月曜日を表します。 他のいくつかのシステムとの互換性のために、 dayofweek 部分は UNIX 標準に従います。 この関数は、曜日を整数値として0-6の範囲で返します。On 29/10/2018 16:26, Andreas Karlsson wrote: > On 10/29/2018 04:18 PM, Vik Fearing wrote: >> A use case that I see quite a lot of is needing to do reports and other >> calculations on data per day/hour/etc but in the user's time zone. EXTRACT (field FROM source) The extract function retrieves subfields such as year or hour from date/time values. DATE_TRUNC (date, < Parameters. PostgreSQL Date Functions Manipulation. CREATE OR REPLACE FUNCTION last_day(date) RETURNS date AS $$ SELECT (date_trunc('MONTH', $1) + INTERVAL. g. SELECT date_trunc ('month', cast (my_date as timestamp)) FROM my_table. You can then manipulate this output (with strftime. ). To group data by year, you can use the DATE_TRUNC function with ‘year’ as the first argument. This example uses TRUNC on a date to truncate it into a month. Use the date_trunc method to truncate off the day (or whatever else you want, e. region, q1.