Question

I have thousands of rows that contain a zipcode attribute with four integers in.
Some rows contain five integers, and some other contain two, or three integers.

What I want to do is to add a 0 before rows that contain only four integers.
The tablename is zipcode and the attribute too.

I want to update the rows and not show them !

I tried this code with no luck (no row affected) :

UPDATE zipcode
SET zipcode = CONCAT('0', zipcode)
WHERE CHAR_LENGTH(zipcode) = 4

Btw, I can use CHAR_LENGTH in a simple select, and it works :

SELECT *
FROM zipcode
WHERE CHAR_LENGTH(zipcode) = 4

So, seems that the CHAR_LENGTH doesn’t work in my WHERE clause.

EDIT: zipcode is an int.

Answer 1

It sounds like you are storing the zipcode as an int, but you really want to treat it as a char.

In that case you have a couple of options:

1) Change the datatype of the column and then execute your update to left pad with 0:

alter table zipcode
  modify column zipcode char(5) not null;

update zipcode
set zipcode = lpad(zipcode,5,'0')
where char_length(zipcode) < 5;

2) Leave the datatype as is, and just format the data on retrieval by left-padding with 0 in the select statement:

select lpad(zipcode,5,'0')
from zipcode;

Demo