答案是:可能走索引也可能不走索引,具体要看列的值可不可为null,Oracle不会为所有列的nullable属性都为Y的sql语句走索引。 例子:
create table t as select * from dba_objects;
CREATE INDEX ix_t_name ON t(object_id, objec…
1.联合索引
测试SQL语句如下:表test中共有4个字段(id, a, b, c),id为主键
drop table test;#建表
create table test(id bigint primary key auto_increment,a int,b int,c int
)#表中插入数据
insert into test(a, b, c) values(1,2,3),(2,3,4),(4,5,…