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The following are examples for DATE_TRUNC( 'field', source) functions − Testdb=# SELECT date_part('hour', INTERVAL '4 hours 3 minutes') The following are examples for DATE_PART( 'field', source) functions − The valid values for field are : microseconds, milliseconds, second, minute, hour, day, week, month, quarter, year, decade, century, millennium The return value is of type timestamp or interval. field selects to which precision to truncate the input value. source is a value expression of type timestamp or interval. This function is conceptually similar to the trunc function for numbers. The valid field names are: century, day, decade, dow, doy, epoch, hour, isodow, isoyear, microseconds, millennium, milliseconds, minute, month, quarter, second, timezone, timezone_hour, timezone_minute, week, year. The field parameter needs to be a string value, not a name. It is a traditional PostgreSQL equivalent to transaction_timestamp().ĭATE_PART(text, timestamp), DATE_PART(text, interval), DATE_TRUNC(text, timestamp) S. It returns the actual current time, but as a formatted text string rather than a timestamp with time zone value. It returns the actual current time, and therefore its value changes even within a single SQL command. It returns the start time of the current statement. It is equivalent to CURRENT_TIMESTAMP, but is named to clearly reflect what it returns.
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PostgreSQL also provides functions that return the start time of the current statement, as well as the actual current time at the instant the function is called. Optionally takes a precision parameter, which causes the result to be rounded to that many fractional digits in the seconds field.Įxamples using the functions from the table above − PostgreSQL provides a number of functions that return values related to the current date and time. The above given PostgreSQL statement will produce the following result −Įxample of the function AGE(timestamp) is − Testdb=# SELECT AGE(timestamp '', timestamp '') When invoked with only the TIMESTAMP as argument, AGE() subtracts from the current_date (at midnight).Įxample of the function AGE(timestamp, timestamp) is − When invoked with the TIMESTAMP form of the second argument, AGE() subtract arguments, producing a "symbolic" result that uses years and months and is of type INTERVAL. Test for finite date, time and interval (not +/-infinity)ĪGE(timestamp, timestamp), AGE(timestamp) S. The following is the list of all important Date and Time related functions available. Interval '1 hour' / double precision '1.5' The following table lists the behaviors of the basic arithmetic operators − Operatorĭouble precision '3.5' * interval '1 hour' Now, let us see the Date/Time operators and Functions. INSERT INTO COMPANY VALUES (10, 'James', 45, 'Texas', 5000.We had discussed about the Date/Time data types in the chapter Data Types. Now, let us create three more records in COMPANY table using the following INSERT statements − This would produce the following result − Testdb=# SELECT NAME, SUM(SALARY) FROM COMPANY GROUP BY NAME
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If you want to know the total amount of salary of each customer, then GROUP BY query would be as follows − ExampleĬonsider the table COMPANY having records as follows − Make sure whatever column you are using to group, that column should be available in column-list. You can use more than one column in the GROUP BY clause. The GROUP BY clause must follow the conditions in the WHERE clause and must precede the ORDER BY clause if one is used. The basic syntax of GROUP BY clause is given below. The GROUP BY clause follows the WHERE clause in a SELECT statement and precedes the ORDER BY clause. This is done to eliminate redundancy in the output and/or compute aggregates that apply to these groups. The PostgreSQL GROUP BY clause is used in collaboration with the SELECT statement to group together those rows in a table that have identical data.