count(1)

Count(1), count(*), order by 1,2,3,4 difference the 1 make NULL data; the the 2 directly use the column name to COUNT to see the result the the 3 Use 1 2 3 4 5 * to COUNT to look at the results and find that they are all the same data and are equal to all functions. www.2cto.com the 4 ORDER BY 1 does use the first column to sort the the 5 ORDER BY 2 See if the result is correct the the result: the count(1)=count(2)=count(3)=count(*); the count(provcode)count(areacode)count(statedate)count(*); the order by 1order by 2oreder by 3; the order by 1=order by provcode the Additional results: the the the Author ZengMuAnSha