Adding specific number of zeros before a string - oracle

Question

I have written this query
update cmart_m_branch
set code=concat('000',cmart_m_branch.code)
where length(code)=1.
But it is not working..it was updating with all zeros..column code should have only 4 characters. But it is working like this.... just I am changing the query.....
Update cmart_m_branch
set code=concat('00',cmart_m_branch.code)
where length(code)=2.
Why it is not working with the length 1 ..please suggest me..

Answer 1

Sounds like you're after LPAD:
WITH sample_data AS (SELECT '1' col1 FROM dual UNION ALL
SELECT '12' col1 FROM dual UNION ALL
SELECT '123' col1 FROM dual UNION ALL
SELECT '1234' col1 FROM dual)
SELECT col1,
LPAD(col1, 4, '0') new_col1
FROM sample_data;
COL1 NEW_COL1
---- --------
1 0001
12 0012
123 0123
1234 1234
Of course, this is assuming that your cmart_m_branch.code column is of string datatype. If it's of number datatype then there is no use in doing the update - you should instead format the data on-the-fly when you're selecting it (or you could use a virtual column to do the formatting for you). This can be done using to_char():
WITH sample_data AS (SELECT 1 col1 FROM dual UNION ALL
SELECT 12 col1 FROM dual UNION ALL
SELECT 123 col1 FROM dual UNION ALL
SELECT 1234 col1 FROM dual)
SELECT col1,
to_char(col1, '0999') new_col1
FROM sample_data;
COL1 NEW_COL1
---------- --------
1 0001
12 0012
123 0123
1234 1234
If you're absolutely dead-set on using concatenation (why?) then you can do it using a case expression:
WITH sample_data AS (SELECT '1' col1 FROM dual UNION ALL
SELECT '12' col1 FROM dual UNION ALL
SELECT '123' col1 FROM dual UNION ALL
SELECT '1234' col1 FROM dual)
SELECT col1,
CASE WHEN LENGTH(col1) = 1 THEN '000'||col1
WHEN LENGTH(col1) = 2 THEN '00'||col1
WHEN LENGTH(col1) = 3 THEN '0'||col1
ELSE col1
END new_col1
FROM sample_data;
COL1 NEW_COL1
---- --------
1 0001
12 0012
123 0123
1234 1234