How to store bitcoin value and other currencies values together in MySql database?
As far as you use a DECIMAL(16, 8) field, values are stored with 6 decimal digits. It doesn't matter if they are bitcoins, euros, dollars, ...

If you want to use a monetary type, then you should take care and properly configure the server just to hold all values.


  8.2. Monetary Types
  
  The money type stores a currency amount with a fixed fractional
  precision; see Table 8.3. The fractional precision is determined by
  the database's lc_monetary setting. The range shown in the table
  assumes there are two fractional digits. Input is accepted in a
  variety of formats, including integer and floating-point literals, as
  well as typical currency formatting, such as '$1,000.00'. Output is
  generally in the latter form but depends on the locale.





CREATE TABLE Amounts(ID int, Value decimal(16,8), Value2 money);

INSERT INTO Amounts VALUES
(1, 100, 100), (2, 12.22636, 12.22636), (3, 0.1, 0.1);

SELECT * FROM Amounts;



✓

3 rows affected

id |        value |   value2
-: | -----------: | -------:
 1 | 100.00000000 | £100.00
 2 |  12.22636000 |  £12.23
 3 |   0.10000000 |   £0.10



dbfiddle here