其实数据库中做了下测试,不知哪位能在MS SQL SERVER上测试一下。mysql> select BENCHMARK(10000000,'aaa' like '___') ; 1 row in set (0.34 sec)mysql> select BENCHMARK(10000000,length('aaa')=3) ; 1 row in set (0.27 sec)
mysql> select BENCHMARK(10000000,'abcdefghijklmnabcdefghijklmnabcdefghijklmnabcdefghijklmn' like '___') ; 1 row in set (0.36 sec)mysql> select BENCHMARK(10000000,length('abcdefghijklmnabcdefghijklmnabcdefghijklmnabcdefghijklmn')=3) ; 1 row in set (0.28 sec)
1 row in set (0.34 sec)mysql> select BENCHMARK(10000000,length('aaa')=3) ;
1 row in set (0.27 sec)
1 row in set (0.36 sec)mysql> select BENCHMARK(10000000,length('abcdefghijklmnabcdefghijklmnabcdefghijklmnabcdefghijklmn')=3) ;
1 row in set (0.28 sec)
为什么?