下面count的返回值是多少？

CREATE TABLE mytable ( myid INT, mychar VARCHAR(10) );GOINSERT mytable        ( myid, mychar )    VALUES        ( 1, 'A' ),        ( 2 , 'B'),        ( NULL, 'C' ),        ( 4, 'D' ),        ( NULL, 'E' ),        ( 6, 'F' );--Query1SELECT COUNT(MyID) FROM mytable;--Query2SELECT COUNT( DISTINCT MyID) FROM mytable; --Query3 SELECT COUNT(DISTINCT *) FROM mytable;

答案

--Query1:4--Query2:4--Query3:ERROR

参考链接：