The number of distinct data in the query table count MySQL Oracle takes the specified number

mysql

The correct way to write it is select count() from (select distinct() from ) a , Note that you must alias the watch a.

limit take 3 strip offset Start with the second one

SELECT count(*) from ( SELECT distinct project from h_record) a

 SELECT distinct project from h_record LIMIT 3 OFFSET 2
 
 select count(*) from (select distinct(*) from ) a

oracle
Take the top ten , Inquire about distinct Quantitative grammar and mysql Agreement

SELECT count(*) from ( SELECT distinct project from h_record) a
 sqlStatement =  f'SELECT * FROM ({
      sqlStatement}) WHERE ROWNUM <=10 '

Take any entry

   sqlStatement =  f'SELECT * FROM (SELECT m.*, ROWNUM NUM FROM ({
      sqlStatement}) m ) WHERE NUM <= 10000 AND num >5000 '

come from Stack Overflow

 SELECT * from
 (
 select m.*, rownum r
 from maps006 m
 )
 where r > 49 and r < 101

Reference resources
https://stackoverflow.com/questions/4552769/sql-rownum-how-to-return-rows-between-a-specific-range

Reference resources
https://blog.csdn.net/ccmedu/article/details/84069311