The ROW_NUMBER function returns the row number over a named or unnamed window specification.
The ROW_NUMBER function does not take any arguments, and for each row over the window it returns an ever increasing BIGINT. It is normally used to limit the number of rows returned for a query. The LIMIT keyword used in other databases is not defined in the SQL standard, and is not supported.
The data type of the returned value is a BIGINT number.
ROW_NUMBER() OVER ()
To limit the number of rows returned from a query to the 10 first rows of table T, use the following query:
SELECT * FROM ( SELECT ROW_NUMBER() OVER () AS R, T.* FROM T ) AS TR WHERE R <= 10;