MySQL GROUP by Regex?

Question

I have the following query

SELECT Count(*) as Total_Count, Col1 
FROM Table1 
GROUP BY Col1 
ORDER BY Total_Count DESC;

I want to zoom in on Col1. The data in Col1 are in the following format:

text-abc1
txt4-abcde22
tex6-abc2
text4-imp4
text-efg1
txt-efg43

I want to be able to group it by

After the first `-`, any first three/four/five characters match

In this example, if we match with first 3 characters. Output will be:

Total_Count   Col1
3             abc
1             imp
2             efg

Any other way to achieve this?

Answer 1

You might not need a regex, just string operations. For three characters:

SELECT count(*) AS Total_Count,
SUBSTRING(Col1 FROM POSITION('-' in Col1)+1 FOR 3) AS Col1_zoomed
FROM Table1
GROUP BY Col1_zoomed
ORDER BY Total_Count DESC

Answer 2

select
substring(substring_index(col1,'-',-1),1,3) as grp,
count(*) as total
from table
group by grp