Similar to indexof usage in oracle _instr function

Similar to indexof usage in oracle _instr function
the
[sql]
There is no indexof() function in oracle
But it provides an instr() method specific usage:
select instr('South District of Baoding City','City',1,1)-1 from dual;
Explanation: 1. ‘South District of Baoding City’ => can be an expression or specific data
    2. ‘市’ => is a sign of separation, here is the word “city” in the two sets of data 
3. The first 1 starts from the left, if it is -1, it starts from the right. the
4. The second 1 is the number of times “city” appears. the
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Under the GBK encoding, a Chinese occupies two bytes
select instr('Baoding South District','city',1,1) from dual; the value is 5
select instr(‘Baoding Nanshi District’, ‘City’,1,2) from dual; the value is 9
the
select instr(‘Baoding Nanshi District’, ‘City’,-1,1) from dual; the value is 9
select instr(‘Baoding Nanshi District’, ‘City’,-1,2) from dual; the value is 5
the
the
Author qyongkang