select count(*)和select (1)"select count(*)返回所有满足条件的记录数,此时同select sum(1) 但是sum()可以传任意数字,负数、浮点数都可以,返回的值是传入值n*满足条件记录数m"1、可以解释下这段话的含

select count和select count的区别 select count(*)count 什么意思和select * 有什么区别 select count(*) from 怎么使用 select count(1) from emp and select 4718 fromselect count $sql=SELECT count(*) as pcount FROM news 和$sql = UPDATE article SET这句是什么意思? count,count和count的区别 SELECT sum(1) FROM table;和SELECT count(1) FROM table;SELECT sum(1) FROM table;----------------累加'1'列的总和;SELECT count(1) FROM table;--------------统计'1'列的总条数;这里总和与总条数有何不同?应该是这样：如果：SE select count(*)和select (1)select count(*)返回所有满足条件的记录数,此时同select sum(1) 但是sum()可以传任意数字,负数、浮点数都可以,返回的值是传入值n*满足条件记录数m1、可以解释下这段话的含 select telnum,count(0),count(distinct othertelnum) from nmk.ljdx_cdr_temp group by telnum select Count(0) from MbrMember where 1=1Count(0)where 1=1 SELECT COUNT(*) FROM Users WHERE Id={0} AND LoginPwd = '{1}' 代码中的小括号和大括号以及单引号表示什么意思 group by 和 distinct 的问题select a.partner as pcode, count(distinct(a.deviceid)) as count -- into num4 from test a where a.activationtime >= to_date('2011-4-17', 'yyyy-mm-dd') and a.activationtime < to_date( select t.*和select *有什么不同 count(0)和count(*)哪个效率高? count(0)和count(*)哪个效率高? select count(*) from table1 select count(*) from table2 select count(*) from table3我从table1 table2 table3 中 找数据的条数怎样一下子用一条sql语句 算出TABLE1 TABLE2 TABLE3 记录的总和? select count (1)V_COUNT := 0;SELECT COUNT(1) INTO V_COUNT FROM CUST WHERE CUST_ID = ARG_CUST_ID;IF V_COUNT = 0 THEN我是个初学者,今有如上这么一段程序,里面select count(1)是什么意思?