Question: I want to extract the part before the 1st `/`, how can I do that?

```
 SELECT REGEXP_SUBSTR('prAct1-03/cPMI-01/iPEPC9-01/t35s-08','(pr.*)/',1,1) as promoter 
   FROM dual;

```

did not work, and seems oracle did not support Lookahead and Lookbehind.
Thanks!

Answer: 
One option uses `REGEXP_REPLACE()` function :

```
SELECT REGEXP_REPLACE('prAct1-03/cPMI-01/iPEPC9-01/t35s-08','(\S)(/.*)','\1') AS promoter
  FROM dual;

```

`[Demo](https://dbfiddle.uk/?rdbms=oracle_11.2&fiddle=95d17d21eca9223566e078a0e00bb0b3)`
Please use below query,

```
select substr('prAct1-03/cPMI-01/iPEPC9-01/t35s-08', 0, instr('prAct1-03/cPMI-01/iPEPC9-01/t35s-08', '/')-1) as promoter from dual;

```

[![enter image description here](https://i.stack.imgur.com/JJHyv.png)](https://i.stack.imgur.com/JJHyv.png)