Get count of zeros in an integer using MySQL - mysql

Question

Let's say I have an integer value in MySQL (10090). I need to count all occurrences of the zero digit in that number. So for the previous case it would return 3:
select count_zeros(number) from dual;
-- when number = 10090, it return 3
-- when number = 10000, it return 4
How can I do that the fastest way using a MySQL query?

Answer 1

You can compare the string length with and without the character you want to count.
Solution using LENGTH
-- 0 in 10090: 3
-- 0 in 10000: 4
SELECT
(LENGTH(number) - LENGTH(REPLACE(number, '0', ''))) AS char_count
FROM dual;
A better and safer solution is to use the CHAR_LENGTH function instead of the LENGTH function. With CHAR_LENGTH function you can also count multi-byte characters (like §).
Solution using CHAR_LENGTH
-- § in 100§0: 1
SELECT
(CHAR_LENGTH(number) - CHAR_LENGTH(REPLACE(number, '§', ''))) AS char_count
FROM dual;
You can also extend the above solution to count for a string value using multiple characters.
-- 12 in 10120012: 2
SELECT number,
FLOOR((CHAR_LENGTH(number) - CHAR_LENGTH(REPLACE(number, '12', ''))) / CHAR_LENGTH('12')) AS str_count
FROM dual;
demo on dbfiddle.uk
On MySQL you can create a function to use the above logic on a simpler way:
CREATE FUNCTION GetStringCount(strValue VARCHAR(255), strSearchValue VARCHAR(255))
RETURNS INT DETERMINISTIC NO SQL
RETURN FLOOR((CHAR_LENGTH(strValue) - CHAR_LENGTH(REPLACE(strValue, strSearchValue, ''))) / CHAR_LENGTH(strSearchValue));
You can use this new function GetStringCount like this:
-- example to count non-multi-byte character (here 0).
-- 0 in 10090: 3
-- 0 in 10000: 4
SELECT number, GetStringCount(number, '0') AS strCount
FROM dual;
-- example to count multi-byte character (here §).
-- § in 100§0: 1
SELECT number, GetStringCount(number, '§') AS strCount
FROM dual;
-- example to count a string with multiple characters.
-- 12 in 10120012: 2
SELECT number, GetStringCount(number, '12') AS strCount
FROM dual;

Answer 2

I think the first thing to be done is, casting those integer values to string.
https://dev.mysql.com/doc/refman/5.7/en/cast-functions.html#function_cast
Then find occurences of a certain char
https://lists.mysql.com/mysql/215049
mysql> create table numbers(x int);
Query OK, 0 rows affected (0,38 sec)
mysql> select * from numbers;
+-----------+
| x |
+-----------+
| 123000 |
| 1300 |
| 135600 |
| 135623400 |
| 13560 |
| 135160 |
| 13514560 |
| 1351120 |
| 13512310 |
+-----------+
9 rows in set (0,00 sec)
Find occurences of zero
mysql> select x, round((length(cast(x as char(11))) - length( replace( cast( x as char(11) ), "0", "" ) ))/length("0")) as str_x from numbers limit 5;
+-----------+-------+
| x | str_x |
+-----------+-------+
| 123000 | 3 |
| 1300 | 2 |
| 135600 | 2 |
| 135623400 | 2 |
| 13560 | 1 |
+-----------+-------+
5 rows in set (0,00 sec)
Find thirteens
mysql> select x, round((length(cast(x as char(11))) - length( replace( cast( x as char(11) ), "13", "" ) ))/length("13")) as str_x from numbers;
+-----------+-------+
| x | str_x |
+-----------+-------+
| 123000 | 0 |
| 1300 | 1 |
| 135600 | 1 |
| 135623400 | 1 |
| 13560 | 1 |
| 135160 | 1 |
| 13514560 | 1 |
| 1351120 | 1 |
| 13512310 | 1 |
| 132134534 | 2 |
+-----------+-------+
10 rows in set (0,00 sec)
mysql>