INSTR() is a string function in standard query language (SQL) which returns the starting position or location of a substring or pattern in the given input string. … SQL INSTR() function returns the first occurrence of a substring in an input string.

What is the use of Instr function?

The INSTR function searches a character string for a specified substring, and returns the character position in that string where an occurrence of that a substring ends, based on a count of substring occurrences.

What is Substr and Instr?

INSTR(PHONE, ‘-‘) gives the index of – in the PHONE column, in your case 4. and then SUBSTR(PHONE, 1, 4 – 1) or SUBSTR(PHONE, 1, 3) gives the substring of the PHONE column from the 1st that has length of 3 chars which is 362 , if the value PHONE column is 362-127-4285 .