How does Number data type work in Oracle 21c?

Question

I created a table like this:

CREATE TABLE table(
    id INTEGER GENERATED ALWAYS AS IDENTITY,
    nome VARCHAR2(100 CHAR)
)    

ALTER TABLE table ADD CONSTRAINT table_pk PRIMARY KEY (ID);

CREATE UNIQUE INDEX TABLE_UNIQ_IDX ON TABLE(NOME ASC);

ALTER TABLE table ADD (PERC NUMBER(1, 2) NOT NULL);

Then I tried to write 2 records on it:

INSERT INTO TABLE(NOME,PERC)VALUES('a',0.8);

INSERT INTO TABLE(NOME,PERC)VALUES('b',0.2);

Then I received this error:

ORA-01438: valor maior que a precisão especificada usado para esta coluna

Translated:

ORA-01438: value larger than specified precision allows for this column

I tried select cast (0.8 as number(1,1)) from dual; and it worked but when I tried select cast (0.8 as number(1,2)) from dual; I received the same error.

I then tried select cast (0.81 as number(1,2)) from dual; and received the same ORA-01438.

I changed my field to number(1,1) , no big deal, but how does this "Number" data type work?

• Shouldn't select cast (0.81 as number(1,2)) from dual; have worked?
• Why does select cast (0.81 as number(2,2)) from dual; work and
• select cast (0.81 as number(2,3)) from dual; does not?

Thanks for any help

Answer 1

What you said, is that perc column should accept numeric values whose length is 1 , and out of that 1 , you want to keep 2 decimal places. That won't work.

SQL> create table test (perc number(1, 2));

Table created.

SQL> insert into test values (0.8);
insert into test values (0.8)
                         *
ERROR at line 1:
ORA-01438: value larger than specified precision allowed for this column

Perhaps you meant to put it vice versa?

SQL> alter table test modify perc number(2, 1);

Table altered.

SQL> insert into test values (0.8);

1 row created.

SQL>

Answer 2

If you have NUMBER(precision, scale) then precision is the number of digits and scale is the number of decimal places.

So, NUMBER(1, 2) has a single digit and 2 decimal places. The minimum value it can store is -0.09 and the maximum it can store is +0.09 .

NUMBER(2,2) works as it stores 2 digits in 2 decimal places (from -0.99 to +0.99).

NUMBER(2,3) does not work as it stores 2 digits in 3 decimal places (from -0.099 to +0.099).