In Oracle, you need to use the `INSTR` perform to verify if a personality exists inside a string. The `INSTR` perform takes two arguments: the substring you wish to discover, and the string you wish to search inside. If the substring is discovered inside the string, the `INSTR` perform will return the place of the primary prevalence of the substring. If the substring is just not discovered, the `INSTR` perform will return 0.
For instance, the next question would verify if the character ‘a’ exists inside the string ‘Good day, world!’: