How to show positions of '1' within a long number mysql - mysql

Question

I know I can find the first position of 1 with my number by using the following:
SELECT POSITION("1" IN "0000100001000001");
How would I find all the positions of 1 to return 5;10;16

Answer 1

Your string appears to be a 16-bit number represented in base-2.
I set a user variable to your example string.
set #bin = '0000100001000001';
We can use CONV() to convert it to a base-10 number instead of base-2. This allows the integer value to be used when we use it in numeric expressions.
mysql> select conv(#bin, 2, 10);
+-------------------+
| conv(#bin, 2, 10) |
+-------------------+
| 2113 |
+-------------------+
Then we can test for a particular bit set in this number using the & bitwise-and operator.
mysql> select conv(#bin, 2, 10) & 64;
+------------------------+
| conv(#bin, 2, 10) & 64 |
+------------------------+
| 64 |
+------------------------+
We can test all the bits of the integer value. If a given bit is set, then substitute the "position," as you call it, for that bit (counting from left to right, which is the opposite of the traditional bit positions).
If the bit is not set, then default to NULL. Then concatenate these together using CONCAT_WS(), which ignores NULLs.
select concat_ws(';',
case conv(#bin,2,10)&32768 when 32768 then 1 end,
case conv(#bin,2,10)&16384 when 16384 then 2 end,
case conv(#bin,2,10)&8192 when 8192 then 3 end,
case conv(#bin,2,10)&4096 when 4096 then 4 end,
case conv(#bin,2,10)&2048 when 2048 then 5 end,
case conv(#bin,2,10)&1024 when 1024 then 6 end,
case conv(#bin,2,10)&512 when 512 then 7 end,
case conv(#bin,2,10)&256 when 256 then 8 end,
case conv(#bin,2,10)&128 when 128 then 9 end,
case conv(#bin,2,10)&64 when 64 then 10 end,
case conv(#bin,2,10)&32 when 32 then 11 end,
case conv(#bin,2,10)&16 when 16 then 12 end,
case conv(#bin,2,10)&8 when 8 then 13 end,
case conv(#bin,2,10)&4 when 4 then 14 end,
case conv(#bin,2,10)&2 when 2 then 15 end,
case conv(#bin,2,10)&1 when 1 then 16 end) as bits_set;
Output:
+----------+
| bits_set |
+----------+
| 5;10;16 |
+----------+

Answer 2

There is no such functionality built in. You can create your own function for this.
delimiter $$
create function f_position_multiple(
in_f char(1),
in_str text
)
returns text
begin
declare v_delim char(1);
declare v_loc int;
declare v_ret text;
set v_ret = '';
set v_delim = '';
set v_loc = 0;
set v_loc = locate(in_f, in_str, v_loc+1);
while(v_loc>0) do
set v_ret = concat(v_ret, v_delim, v_loc);
set v_delim = ';';
set v_loc = locate(in_f, in_str, v_loc+1);
end while;
return v_ret;
end
$$
And then you can use:
select f_position_multiple('1', '1001001')

Answer 3

A solution for MySql 8.0+ with a recursive CTE:
set #n = '0000100001000001';
with recursive cte as (
select 0 pos, ' ' bit
union all
select pos + 1, substring(#n, pos + 1, 1)
from cte
where pos < length(#n)
)
select group_concat(pos order by pos separator ';') result
from cte
where bit = '1'
See the demo.
Result:
| result |
| ------- |
| 5;10;16 |