What is a regular expression? A regular expression is reduced as regex or regexp. It is a sequence of characters that specifies a search method (they are patterns in regex). It can be called rational expression also. In regex, each character is in a string describing its pattern. String-searching algorithms are used in this method to “find” or “find and replace” operations on strings, or for input validation.
Many search engines use regex to search the patterns and some of the programming languages provide regex capabilities either built-in or via libraries, as it has uses in many situations.
An example of a regular expression is
Expression of word customizable – customi[sz]able
Matches both “customizable” and “customisable”
The regular expression ^[ \S]+|[ \S]+$ matches excess whitespace at the beginning or end of a line and extra change in line. An advanced regular expression that matches any numeral is \b””\b[+-]?(\d+(\.\d+)?|\.\d+)([eE][+-]?\d+)?
The regular expression in Bigquery
Regular expression in bigquery used to validate the query used in Google Cloud Platform(GCP). Regex specifies a search pattern for query used in bigquery services.
While using this service, users have to validate the query to get the desired result. Regex is the best option to check your query.
For example:
For SQL query:
By validating this query directly can give an error result of this query. As the json of this SQL query will be:
To validate some part of this query we have to use regex. The regular expression of this subqueries will be:
By using regex a user can ignore space, new line or carriage return.
