How to intercept string in oracle

There are three ways to intercept strings in Oracle: SUBSTR function: extract substrings based on the starting position and length. INSTR function: Determine the position where the substring appears, and intercept the string with the SUBSTR function. REGEXP_SUBSTR function: Extract substrings from strings using regular expressions.

Methods for intercepting strings in Oracle

In Oracle, there are the following methods for intercepting strings:

1. SUBSTR function

SUBSTR function extracts a substring from a string. The syntax is as follows:

<code>SUBSTR(string, start_position, length)</code>

• string is the string to be intercepted.
• start_position is the position where the substring starts.
• length is the length of the substring.

Example:

Intercept the string "Hello World" from the 4th character to the 7th character:

<code>SUBSTR('Hello World', 4, 4)</code>

Result: "Worl"

2. INSTR function

The INSTR function returns the first position where the substring appears in the string. The syntax is as follows:

<code>INSTR(string, substring, start_position, occurrence)</code>

• string is the string to search for.
• substring is the substring to be found.
• start_position (optional) is the starting position of the search. Defaults to 1, indicating the beginning of the string.
• occurrence (optional) is the matching substring number. Defaults to 1, indicating the first match.

Example:

Find the position of the substring "Hello" in the string "Hello World, Hello Oracle":

<code>INSTR('Hello World, Hello Oracle', 'Hello')</code>

Result: 1

After using the INSTR function to determine the position of the substring, you can combine it with the SUBSTR function to intercept the string.

3. REGEXP_SUBSTR function

The REGEXP_SUBSTR function uses regular expressions to extract substrings from strings. The syntax is as follows:

<code>REGEXP_SUBSTR(string, pattern, position, occurrence, flags)</code>

• string is the string to be intercepted.
• pattern is a regular expression pattern.
• position (optional) is the sequence number of the returned substring. Defaults to 1, indicating the first match.
• occurrence (optional) is the matching substring number. Defaults to 1, indicating the first match.
• flags (optional) are regular expression flags.

Example:

Use the REGEXP_SUBSTR function to intercept the numeric part from the string "Hello123World":

<code>REGEXP_SUBSTR('Hello123World', '[0-9]+')</code>

Result: "123"

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