JPAQuery query = new JPAQuery(getEntityManager()).select(myTable).from(myTable).where(template. You can use various datetime expressions or a user-defined DATEDIFF function (UDF) to calculate the difference between 2 datetime values in seconds, minutes, hours, days, weeks, months and years in PostgreSQL. QMyTable myTable = QMyTable.myTable įinal NumberTemplate template = Expressions.numberTemplate(Integer.class, "function('datediff', )", myTable.date1, myTable.date2) SELECT UserName, MAX ( LoginDateTime) AS LoginDateTime, (DATEDIFF (DAY, MAX ( LoginDateTime), GETDATE ())) as datediff FROM Login GROUP BY UserName. This template is then easily usable in the next query. Try this, if you want to get the latest login for each user. The datediff Function plays an important role in the database management system because datediff functions as a calendar and is very helpful to users. The datediff means we can return the difference between two dates based on their specified interval. You can use the static methods in class Expressions to create such templates. PostgreSQL provides a datediff function to users. This post presents a comprehensive guide on calculating the difference between different dates, times, timestamps, and intervals using examples. You just have to define a template, especially a number template in this example. In PostgreSQL, the - operator, DATEPART (), EXTRACT (), and AGE () functions are used to calculate the difference between various DateTime values.
#Postgresql datediff how to
So you can use this function with two simple parameters.īut how to use this function in QueryDSL? This is quite easy. I used a custom function to solve this problem: CREATE OR REPLACE FUNCTION datediff(a TIMESTAMP, b TIMESTAMP) RETURNS integer AS $$ So you have the problem to subtract one date or timestamp from another. JPA only supports to call functions with simple parameters, but not the calculation of two dates. Hortonworks Hadoop Hive, MapR Hadoop Hive, MySQL, Oracle, PostgreSQL, and Tableau extracts. In PostgreSQL you would use date_part like: SELECT DATE_PART('day', date2 - date1) FROM mytable DATEDIFF(month, date joined band, date left band). So you have to use native database functions. Unfortunately JPA or JQL currently did not support a date difference function.
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