INSTR FAQS

 1. What does the INSTR function return if the substring is not found?

·         If the substring is not found, the INSTR function returns 0.

Example:

SELECT INSTR('Hello World', 'Oracle') FROM dual;

Output: 0 (since Oracle is not found in Hello World).

 

2. Is the INSTR function case-sensitive?

·         Yes, the INSTR function is case-sensitive. It only matches substrings that exactly match in case.

Example:

SELECT INSTR('Hello World', 'world') FROM dual;

Output: 0 (since world does not match World in case).

 

3. How does the INSTR function behave if a NULL value is passed?

·         If any argument (string, substring, or start_position) is NULL, the INSTR function will return NULL.

Example:

SELECT INSTR(NULL, 'World') FROM dual;

Output: NULL

 

4. Can I use INSTR to find the position of a character in a string?

·         Yes, you can use INSTR to find the position of a single character by passing that character as the substring.

Example:

SELECT INSTR('Hello World', 'o') FROM dual;

Output: 5 (The first occurrence of o is at position 5).

 

5. How does the INSTR function handle spaces in the string?

·         Spaces are treated like any other character. If you want to find the position of a space, pass a space character (' ') as the substring.

Example:

SELECT INSTR('Hello World', ' ') FROM dual;

Output: 6 (Space is found at position 6).

 

6. Can INSTR find multiple occurrences of a substring?

·         No, INSTR only finds the first occurrence of the substring. However, you can use the match_occurance parameter to find subsequent occurrences.

Example:

SELECT INSTR('Hello World, Hello Universe', 'Hello', 1, 2) FROM dual;

Output: 14 (Second occurrence of Hello).

 

7. How do I search from the end of the string using INSTR?

·         You can search from the end of the string by passing a negative value for the start_position.

Example:

SELECT INSTR('Hello World, Hello Universe', 'Hello', -1) FROM dual;

Output: 14 (Last occurrence of Hello starting from the end).

 

8. Can INSTR be used with other functions like SUBSTR or REPLACE?

·         Yes, INSTR can be used in combination with other string functions, such as SUBSTR, to extract parts of a string or REPLACE to manipulate text.

Example:

SELECT SUBSTR('Hello World', INSTR('Hello World', 'World')) FROM dual;

Output: World (Extracts the substring starting from World).

 

9. Can INSTR handle patterns or wildcards?

·         No, INSTR does not support wildcards or patterns. For pattern-based matching, you should use REGEXP_INSTR.

Example using REGEXP_INSTR:

SELECT REGEXP_INSTR('Hello World 123', '\d') FROM dual;

Output: 13 (Position of the first digit in the string).

 

10. What happens if INSTR is used with a negative start_position?

·         If start_position is negative, INSTR will start counting from the end of the string. For example, -1 means the function starts searching from the last character.

Example:

SELECT INSTR('Oracle Database', 'a', -3) FROM dual;

Output: 9 (Finds the a starting from the third-to-last character).

 

11. Is it possible to use INSTR with an empty string?

·         If the string is empty (''), INSTR will return 0, as there are no characters to find the substring.

Example:

SELECT INSTR('', 'Hello') FROM dual;

Output: 0 (No substring found in the empty string).

 

12. Can INSTR be used with columns in a table?

·         Yes, INSTR can be used to search for substrings within columns in a table. You can use it to find specific patterns or characters in column values.

Example:

SELECT INSTR(email, '@') FROM users;

Output: Returns the position of @ in each email address in the user’s table.