解读Oracle中代替like进行模糊查询的方法instr(更高效)

instr(sourceString,destString,start,appearPosition)     

--从开头开始查找第一个‘h'出现的位置
select instr('zhangsan', 'h') as idx from dual; --2

--从开头开始查找‘an'在字符串中的位置
select instr('zhangsan','an') idx from dual; --3

--从第一个位置开始查找，返回第二次出现‘a'的位置
select instr('zhangsan','a',1,'2') idx from dual; --7

--从倒数第一个位置开始，查找第一次出现‘a'的位置
select instr('zhangsan','a',-1,1) idx from dual;  --7

--从倒数第一个位置开始，返回第二次出现‘a'的位置
select instr('zhangsan','a',-1,2) idx from dual;   --3

with temp1 as (
select 'zhangsan' as name from dual),
temp2 as (
select 'zhangsi' as name from dual),
temp3 as (
select 'xiaoming' as name from dual),
temp4 as (
select 'xiaohong' as name from dual),
temp5 as (
select 'zhaoliu' as name from dual)
 
select * from (select * from temp1 
union all
select * from temp2
union all
select * from temp3
union all
select * from temp4
union all
 
select * from temp5) res where res.name like '%zhang%'

with temp1 as (
select 'zhangsan' as name from dual),
temp2 as (
select 'zhangsi' as name from dual),
temp3 as (
select 'xiaoming' as name from dual),
temp4 as (
select 'xiaohong' as name from dual),
temp5 as (
select 'zhaoliu' as name from dual)
 
select * from (select * from temp1 
union all
select * from temp2
union all
select * from temp3
union all
select * from temp4
union all
 
 
select * from temp5) res where instr(res.name,'zhang') > 0;

with temp1 as (
select 'zhangsan' as name from dual),
temp2 as (
select 'zhangsi' as name from dual),
temp3 as (
select 'xiaoming' as name from dual),
temp4 as (
select 'xiaohong' as name from dual),
temp5 as (
select 'zhaoliu' as name from dual)
 
select * from (select * from temp1 
union all
select * from temp2
union all
select * from temp3
union all
select * from temp4
union all
 
select * from temp5) res where instr(res.name,'zhang') = 0;

with temp1 as (
select 'zhangsan' as name from dual),
temp2 as (
select 'zhangsi' as name from dual),
temp3 as (
select 'sizhangsan' as name from dual),
temp4 as (
select 'xiaohong' as name from dual),
temp5 as (
select 'zhaoliu' as name from dual)
 
select * from (select * from temp1 
union all
select * from temp2
union all
select * from temp3
union all
select * from temp4
union all
 
 
select * from temp5) res where instr(res.name,'zhang') = 1;

select id, name from users where instr('a, b', id) > 0;
--等价于
select id, name
  from users
 where id = a
    or id = b;
--等价于
select id, name from users where id in (a, b);

--创建10万条测试数据
create table test_instr_like as 
select rownum as id,'zhangsan' as name 
from dual
connect by level <= 100000;
 
--name列建立索引
create index idx_tb_name on test_instr_like(name);

select * from TEST_INSTR_LIKE t where t.name like '%zhang%'

select * from TEST_INSTR_LIKE t where instr(t.name, 'zhang') > 0;