What is the function of the SQL INSTR function?

The INSTR function in SQL is used to find the position of the first occurrence of one string within another string, and returns its position index. The syntax of the function is as follows:

INSTR(string, substring, start, occurrence)

The parameters are as follows: string – the string to search within. substring – the subtring to search for within the string. start – specifies the position to begin the search. If not specified, it defaults to starting at the first character. occurrence – specifies which occurrence of the substring to return. If not specified, it defaults to returning the position of the first occurrence. The INSTR function returns an integer representing the position index of the substring within the original string. If the substring is not found, it returns 0.