Oracle queries do not display 0 before the decimal point

1. The origin of the problem
When the Oracle database field value is less than 1 decimals, processing with char type loses 0 of the preceding decimal point
For example, 0.35 becomes. 35
2. WORKAROUND: Format the digital display with the TO_CHAR function
Select To_char (0.338, ' fm9999999990.00 ') from dual;
Results: 0.34
The focus here is to see the fm9999999999.99, which means that the integer part is up to 10 bits, the fractional part is 2 bits, and the FM indicates that the space before the transpose string is removed, and there are spaces before the fm,0.34.

Use of 3.with
With TMP1 as (
SELECT 1 as A, 2 as B from DUAL
UNION
SELECT 1 as A, 3 as B from DUAL
UNION
SELECT 1 as A, 4 as B from DUAL
),
TMP2 as (
SELECT 1 as A, 2 as B from DUAL
UNION
SELECT 1 as A, 3 as B from DUAL
UNION
SELECT 2 as A, 4 as B from DUAL
)
SELECT tmp1.*,tmp2.*
From TMP1 JOIN TMP2
On TMP1. A = TMP2. A

The author "strives forward"

After testing, the suspect is the number to char, the 0 before the decimal point

[SQL]View Plaincopy

2. sql> Select To_char (num,' 999999999.999999999 ') from ml_test;
6. To_char (NUM, ' 999999999.9999999
8. ------------------------------
10. .421240000
12. .421246543
14. 65432.421243240
16. 4.621240000
20. sql> Select To_char (num) from ml_test;
24. To_char (NUM)
26. ----------------------------------------
28. .42124
30. .4212465434
32. 65432.42124324
34. 4.62124
38. sql> Select To_char (0.99) from dual;
42. To_char (0.99)
44. -------------
46. .99

--4. How to solve the solution as follows

(1)

[SQL]View Plaincopy

2. sql> Select To_nmber (To_char (0.99)) from dual;
6. To_number (To_char (0.99))
8. ------------------------
10. 0.99
14. sql> Select To_char (num,' fm999999990.999999999 ') from ml_test;
18. To_char (NUM, ' FM999999990.99999
20. ------------------------------
22. 0.42124
24. 0.421246543
26. 65432.42124324
28. 4.62124

(2) Using the case or Decode function, take the first digit is ".", 0, OK.

[SQL]View Plaincopy

2. sql> Select To_char (num,' 999999999.999999999 ') from ml_test;
6. To_char (NUM, ' 999999999.9999999
8. ------------------------------
10. .421240000
12. .421246543
14. 65432.421243240
16. 4.621240000
20. sql> Select To_char (num) from ml_test;
24. To_char (NUM)
26. ----------------------------------------
28. .42124
30. .4212465434
32. 65432.42124324
34. 4.62124
38. sql> Select To_char (0.99) from dual;
42. To_char (0.99)
44. -------------
46. .99

Oracle queries do not display 0 before the decimal point