create table t1 (a decimal(10,4) not null, primary key(a)) engine='InnoDB' 
partition by key (a) (
partition pa1 max_rows=20 min_rows=2,
partition pa2 max_rows=30 min_rows=3,
partition pa3 max_rows=30 min_rows=4,
partition pa4 max_rows=40 min_rows=2);
show create table t1;
Table	Create Table
t1	CREATE TABLE `t1` (
  `a` decimal(10,4) NOT NULL,
  PRIMARY KEY (`a`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1
/*!50100 PARTITION BY KEY (a)
(PARTITION pa1 MAX_ROWS = 20 MIN_ROWS = 2 ENGINE = InnoDB,
 PARTITION pa2 MAX_ROWS = 30 MIN_ROWS = 3 ENGINE = InnoDB,
 PARTITION pa3 MAX_ROWS = 30 MIN_ROWS = 4 ENGINE = InnoDB,
 PARTITION pa4 MAX_ROWS = 40 MIN_ROWS = 2 ENGINE = InnoDB) */
insert into t1 values (999999.9999), (-999999.9999), (123456.7899), (-123456.7899), (-1.5), (1), (0), (-1), (1.5), (1234.567), (-1234.567);
select * from t1;
a
-999999.9999
-123456.7899
-1234.5670
-1.5000
-1.0000
0.0000
1.0000
1.5000
1234.5670
123456.7899
999999.9999
select * from t1 where a=1234.567;
a
1234.5670
delete from t1 where a=1234.567;
select * from t1;
a
-999999.9999
-123456.7899
-1234.5670
-1.5000
-1.0000
0.0000
1.0000
1.5000
123456.7899
999999.9999
drop table t1;
create table t2 (a decimal(18,9) not null, primary key(a)) engine='InnoDB' 
partition by key (a) partitions 10;
show create table t2;
Table	Create Table
t2	CREATE TABLE `t2` (
  `a` decimal(18,9) NOT NULL,
  PRIMARY KEY (`a`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1
/*!50100 PARTITION BY KEY (a)
PARTITIONS 10 */
insert into t2 values (999999999.999999999), (-999999999.999999999), (-1.5), (-1), (0), (1.5), (1234.567), (-1234.567);
select * from t2;
a
-999999999.999999999
-1234.567000000
-1.500000000
-1.000000000
0.000000000
1.500000000
1234.567000000
999999999.999999999
select * from t2 where a=1234.567;
a
1234.567000000
delete from t2 where a=1234.567;
select * from t2;
a
-999999999.999999999
-1234.567000000
-1.500000000
-1.000000000
0.000000000
1.500000000
999999999.999999999
delete from t2;
1024*3 inserts;
select count(*) from t2;
count(*)
3072
drop table t2;