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# INSTR

## Syntax

```sql
INSTR(string, substring [, position [, occurrence]])
```

## Ovrview

`INSTR` is a function that searches for *substring* in *string*. The search operation works by sequentially comparing substrings of the same length as the target substring within the given string to check for a match. The search can proceed either forward or backward, with each new substring starting one character after (or before, in backward search) the previous one. If a matching substring is found, the function returns an integer indicating the position of the first character of the match. If no match is found, it returns 0.

#### Parameter

| Parameter         | Description                                                                                                                                                                                                                    |
| ----------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| string, substring | Arbitrary operations that all return strings. If the string substr is not found within the string str, 0 is returned. The position value of the string starts from 1.                                                          |
| position          | Arbitrary operation that returns a non-zero integer value. (Default: 1) If position is given, search starts from the position of the string str. If position is negative, search starts from the end of the string str.        |
| occurrence        | Arbitrary operation that returns an integer value other than 0. (Default: 1) Given occurrence, returns the position of substr, which appears occurrence times within the search string. occurrence must be a positive integer. |

## **Example**

```sql
SELECT INSTR('ABCDEABCDEABCDE', 'CD');
 instr 
-------
     3
```


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