Redshiftのdecimalの数値計算時の注意点

drop table test;
create table test(a decimal(8,2), b decimal(8,7),c decimal(38,23));
insert into test values(1,3,null);

select * from test;
insert into test(c) select a/b from test;
select * from test;

mydb=# drop table test;
DROP TABLE
mydb=# create table test(a decimal(8,2), b decimal(8,7),c decimal(38,23));
CREATE TABLE
mydb=# insert into test values(1,3,null);
INSERT 0 1
mydb=# 
mydb=# select * from test;
  a   |     b     | c 
------+-----------+---
 1.00 | 3.0000000 |  
(1 row)

mydb=# insert into test(c) select a/b from test;
INSERT 0 1
mydb=# select * from test;
  a   |     b     |             c             
------+-----------+---------------------------
 1.00 | 3.0000000 |                          
      |           | 0.33330000000000000000000
(2 rows)