Question

I have a mysql table in which there is a column e.g. called name. The column data has a specific pattern nameBase+number. E.g.

name
----------
test0
test1
test2
stack0
stack1
stack2

Each time I want to add data to the column, I have to find the last number for specific nambeBase and add the new entry +number+1.

For example, if now test came, I have to add test3 to db.

My question: What is the best way to 1. check if the nameBase already exists in db(sth like contains) and 2.find the last nameBase number. E.g. here for test is 3.

Update : Everyone, one update. I finally used java Pattern class. So cool and easy. It made everything so simple. I just could add the /d to pattern and then I could check if that matches the name and could use the pattern group to easily access the second part.

Answer 1

The real solution here is to change the database schema to split this into two columns, the name and its number. It becomes trivial then to get the aggregate MAX() via

SELECT name, MAX(num) AS num FROM tbl GROUP BY name

However,if changing it is not an option, I would recommend using REPLACE() to remove the name portion from the column value leaving only the number portion when querying, and get the aggregate MAX() of that to find the highest existing number for it:

SELECT
  MAX(REPLACE(name, <the name to search>, '')) AS maxnum
FROM tbl
WHERE 
  name LIKE '<the name to search>%'

Or instead of LIKE, using a regular expression, which is more accurate than LIKE (in case a name contains another name, the LIKE might match) but more expensive:

SELECT
  MAX(REPLACE(name, <the name to search>, '')) AS maxnum
FROM tbl
WHERE 
  name REGEXP '^<the name to search>[0-9]+$'