Redshift substring regex12/17/2023 ![]() ![]() Huy Nguyenĭata Engineer turned Product writes SQL for a living. Join 15k+ people to get insights from BI practitioners around the globe. Having problems finding a simple and affordable data reporting system for your startups? Check us out at holistics.io. I've compiled the list of examples with sample data here for your reference (you can copy and paste directly into your SQL terminal) Working with array in Redshift and MySQL is usually a pain, but most of the times there's always creative workaround that helps you achieve the same purpose! Inner join books B ON NS.n <= JSON_ARRAY_LENGTH(B.tags) TRIM(JSON_EXTRACT_ARRAY_ELEMENT_TEXT(B.tags, NS.n - 1)) AS val ![]() Or you can use some JSON array functions: with NS AS ( One approach is you can just treat them as string, and apply the same string_split above with some string cleaning (remove quotes, square brackets). Okay, what if your tags column is actually a string that contains a JSON string? tags (string with json) I am thinking of substring etc, but I only have regexpsubstr available right now. Edit: Trying out the below, but it only returns 051-a92 where as I need 05192 as output. What if I have an Redshift JSON array instead? It is hard here as Redshift do not support functions and is missing lot of traditional functions. MySQL doesn't have REGEXP_COUNT, so we have to work around a bit to count the number of, in the string.MySQL doesn't have SPLIT_PART, so we use 2 nested SUBSTRING_INDEX to achieve the same thing You’re probably struggling with meaning something in regular expressions (lookup back references) To tell regex that you just mean the characters (and ) without their special meaning, escape them using \ regexpsubstr(yourtable.yourcolumn,'\(.MySQL doesn't have CTE, so you have to write NS as a subquery.Inner join books B ON NS.n <= CHAR_LENGTH(B.tags) - CHAR_LENGTH(REPLACE(B.tags, ',', '')) + 1 TRIM(SUBSTRING_INDEX(SUBSTRING_INDEX(B.tags, ',', NS.n), ',', -1)) as tag Similar approach can be applied if you're using MySQL, though you have to change up the syntax/functions a little bit: select Here, the NS (number sequence) is a CTE that returns a list of number from 1 to N, here we have to make sure that our max number is greater than the size of our maximum tags, so you can try adding more numbers to the list depending on your context. The above query will give you the exact results as using unnest in Postgres. Inner join books B ON NS.n <= REGEXP_COUNT(B.tags, ',') + 1 TRIM(SPLIT_PART(B.tags, ',', NS.n)) AS tag The solution (or workaround) is trying to split the string into multiple part: with NS AS ( In Postgres, we can immediately use unnest: select TRIM( UNNEST( STRING_TO_ARRAY(tags, ',') ) ) from books īut how do we do this in Amazon Redshift (that doesn't support unnest)? String to Array in Amazon Redshift Regular expression Denial of Service - ReDoS Reset/Forgotten Password Bypass. Suppose we have a books table in Amazon Redshift that has these data: tags (varchar)Īnd we want to split/unnest/explode it so that it becomes like this tag 5439 - Pentesting Redshift 5555 - Android Debug Bridge 5601 - Pentesting. prefixing / and apply the regular expression to extract the step. Question - Splitting comma-delimited string into rows in Redshift Redshift REGEXPSUBSTR get last occurrence of a match. Today, one of our customers came to us with a question - They were having problems unnesting a string/array into rows in Amazon Redshift. And from time to time they come to us with SQL question - that we thought would be interesting to share with others! One last note, SQL split functions on data warehouses is resource and time consuming task because databases like Redshift are produced for aggregations not for string processing.We've worked with a lot of customers who writes SQL on a regular basis. The result of executing above SQL Select query on Redshift table with sample data contains 16 rows each mapping to a part of concatenated list column values.Īs seen in this Redshift SQL tutorial, although it is a bit confusing, splitting string on Redshift database is possible. Split_part(tbl.list, ',', numbers.num::int) as t ![]()
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