In PostgreSQL the last_value() function returns the value from the last row of the current window frame.
Tag: functions
Using the FIRST_VALUE() Function to Get the Value from the First Row in PostgreSQL
In PostgreSQL the first_value() function returns the value from the first row in the current window frame.
We can use this function to get the value from the first row in a result set, or from the first row in the current partition, or some other window frame that’s been specified.
Continue readingUnderstanding the sys.ps_is_consumer_enabled()Â Function in MySQL
In MySQL, we can use the sys.ps_is_consumer_enabled() function to check whether a given Performance Schema consumer is enabled.
The function returns YES or NO, depending on whether or not the specified Performance Schema consumer is enabled. It returns NULL if the argument is NULL.
Overview of the MODE() Function in PostgreSQL
PostgreSQL has an ordered-set aggregate function called mode() that allows us to get the mode from a given column.
The mode is the most frequently occurring value.
Null values are ignored, so if null occurs the most, the mode() function will return the second most common value.
Overview of the MEDIAN() Function in MariaDB
In MariaDB, the MEDIAN() function returns the median value of a range of values.
We can use the MEDIAN() function in our queries to get a column’s median value across its partition or the whole result set.
Understanding the PERCENTILE_DISC() Function in SQL Server
In SQL Server, PERCENTILE_DISC() is a window function that returns a percentile value based on a discrete distribution of the input column. Basically, it returns the first value in the set whose ordered position is the same or more than the specified fraction.
The output of PERCENTILE_DISC() is equal to a specific column value (unlike the PERCENTILE_CONT() function, which could calculate a value that isn’t in the column).
When we call PERCENTILE_DISC() we specify the percentile to use. It then performs its calculation based on that percentile.
Understanding the PERCENTILE_CONT() Function in SQL Server
In SQL Server, PERCENTILE_CONT() is a window function that calculates a percentile based on a continuous distribution of the column value.
When we call the function, we specify the percentile to use. It then performs its calculation based on that percentile.
Continue readingHow to Use the LEAD() Function in SQL Server
In SQL Server, LEAD() is a window function that allows us to access a value from a later row in the same result set, without the need to perform a self-join.
We specify the row as an offset from the current row. An offset of 1 means it gets the value from the next row, an offset of 2 means two rows forward, and so on.
Introduction to the LAG() Function in SQL Server
In SQL Server, LAG() is a window function that enables us to access a value from a previous row in the same result set, without the need to perform a self-join.
We specify the previous row as an offset from the current row. An offset of 1 means the previous row, an offset of 2 means two rows back, and so on.
How to Use the LAST_VALUE() Function in SQL Server
In SQL Server, the LAST_VALUE() function returns the last value in an ordered set of values.
LAST_VALUE() is a window function that enables us to get a value from the last row of a query result set or partition. This can be useful for when we want to do stuff such as compare a value from the current row with a value in the last row or include it in a calculation.
You may need to explicitly set the window frame if you want LAST_VALUE() to return the actual last value from the partition or result set. That’s because the default window frame ends with the current row. This is covered in the example below.