Syntax
------

DECIMAL[(M[,D])] [SIGNED | UNSIGNED | ZEROFILL]

Description
-----------

A packed "exact" fixed-point number. M is the total number of digits (the
precision) and D is the number of digits after the decimal point (the scale).

* The decimal point and (for negative numbers) the "-" sign are not
counted in M. 
* If D is 0, values have no decimal point or fractional
part and on INSERT the value will be rounded to the nearest DECIMAL. 
* The maximum number of digits (M) for DECIMAL is 65. 
* The maximum number of supported decimals (D) is 30 before MariadB 10.2.1 and
38 afterwards. 
* If D is omitted, the default is 0. If M is omitted, the default is 10.

UNSIGNED, if specified, disallows negative values.

ZEROFILL, if specified, pads the number with zeros, up to the total number of
digits specified by M.

All basic calculations (+, -, *, /) with DECIMAL columns are done with a
precision of 65 digits.

For more details on the attributes, see Numeric Data Type Overview.

DEC, NUMERIC and FIXED are synonyms, as well as NUMBER in Oracle mode from
MariaDB 10.3.

Examples
--------

CREATE TABLE t1 (d DECIMAL UNSIGNED ZEROFILL);

INSERT INTO t1 VALUES (1),(2),(3),(4.0),(5.2),(5.7);
Query OK, 6 rows affected, 2 warnings (0.16 sec)
Records: 6  Duplicates: 0  Warnings: 2

Note (Code 1265): Data truncated for column 'd' at row 5
Note (Code 1265): Data truncated for column 'd' at row 6

SELECT * FROM t1;
+------------+
| d          |
+------------+
| 0000000001 |
| 0000000002 |
| 0000000003 |
| 0000000004 |
| 0000000005 |
| 0000000006 |
+------------+

With strict_mode set, the default from MariaDB 10.2.4:

INSERT INTO t1 VALUES (-7);
ERROR 1264 (22003): Out of range value for column 'd' at row 1

With strict_mode unset, the default until MariaDB 10.2.3:

INSERT INTO t1 VALUES (-7);
Query OK, 1 row affected, 1 warning (0.02 sec)
Warning (Code 1264): Out of range value for column 'd' at row 1

SELECT * FROM t1;
+------------+
| d          |
+------------+
| 0000000001 |
| 0000000002 |
| 0000000003 |
| 0000000004 |
| 0000000005 |
| 0000000006 |
| 0000000000 |
+------------+

URL: https://mariadb.com/kb/en/decimal/