SQL Convert character to numeric

Question

I have a have a column which is set as character but users can insert numbers.

How can I identify when the field has numbers length 11 and not letters?

Example:

sample data {col1= aaaaaaaaaaa,11111122222}

select Col1
from
table
group by 1
having SUM(CHARACTER_LENGTH(Col1))=11

wrong output: aaaaaaaaaa

desired output: 11111122222

In short, I need to retrieve all values in the char column that could be identified as numbers and having 11 digits.

Answer 1

With similar to and character_length():

select * from tablename
where (col similar to '[0-9]+') and character_length(col) = 11

or:

select * from tablename
where col similar to '[0-9]{11}'

See the demo.