oracle count over partition by,over （Partition by...） of oracle

The "COUNT OVER PARTITION BY" clause in Oracle is used to calculate the count of rows within a specific partition or group of rows. The "PARTITION BY" clause is used to divide the result set into partitions based on one or more columns. The "OVER" clause is used to specify the window or range of rows that the function should operate on.

Here is an example of how to use "COUNT OVER PARTITION BY" in Oracle:

SELECT column1, column2, COUNT(*) OVER (PARTITION BY column1) as count_column1
FROM table_name;

This query will return the count of rows for each unique value in column1. The "OVER (PARTITION BY column1)" clause specifies that the count should be calculated within each partition of rows that have the same value in column1.