subquery_select_from_select.sql

来自「AbsDataBase5.16 最新版」· SQL 代码 · 共 8 行

/*This SQL script uses Demos.abs database. 
  Please open ...\AbsoluteDatabase\Demos\Data\Demos.abs database file.
  This sample illustrates use of a subquery in FROM clause. 
  The subquery retrieves count of unique names in table "Employee", then function "count" counts quantity of these names.*/


select count(*) UniqueNamesCount from (select distinct FirstName from Employee)