//**1.设置选中值:(根据索引确定选中值)**// var osel=document.getElementById("selID"); //得到select的ID var opts=osel.getElementsByTagName("option");//得到数组option var obt=document.getElementById("bt"); obt.onclick=function(){ opts[3].selected=tr
1. SELECT语句的子查询 语法: SELECT ... FROM (subquery) AS name ... 先创建一个表: CREATE TABLE t1 (s1 INT, s2 CHAR(5), s3 FLOAT);INSERT INTO t1 VALUES (1,'1',1.0);INSERT INTO t1 VALUES (2,'2',2.0); 我们就可以进行以下的嵌套查询了:SELECT sb1,sb2,sb3 FROM (SELECT s1 AS sb1