How to copy a Number column to VARCHAR column with leading and trailing zeros - oracle10g

I am trying to copy Number column to VARCHAR column but its removing leading and trailing zeros. I tried with below update SQL.
UPDATE Employee SET Salary_char = TO_CHAR(salary_num);
But its removing leading and trailing zeros. if value is 0.20 it persists .2
How to avoid this.


You need to provide a suitable number format model for your call to to_char(), e.g.
UPDATE Employee SET Salary_char = TO_CHAR(salary, '9999990.00')
with enough leading 9s to allow the highest value you can have in the original column.


Below update worked for me. It update number column values as it is in varchar column.
UPDATE Employee SET Salary_char = TO_NUMBER(salary_num);

Related

How to update records in a table to trim whitespaces in JSON datatype of Postgres for a specific field

I have a requirement to update a table by TRIM whitespace for a specific column which is a JSON datatype.
In the screenshot is the data structure of the table and the column I have to update is SCOPE
Inside SCOPE I have to TRIM the field SITES and as example a screenshot of the testing table
In the above screenshots, I have to TRIM only sites using an update as I need to build a migration function which for every row will TRIM from SITES the white spaces.
I have no clue in JSONB type how to do it.
UPDATE screenshot of the leading whitespace in data

Use jsonb_array_elements_text on the sites, trim each value, then jsonb_aggregate them back to an array.
UPDATE data
SET scope = jsonb_set(scope, '{sites}', (
SELECT jsonb_agg(trim(site))
FROM jsonb_array_elements_text(scope->'sites') AS s(site)
));
(online demo)
Since Postgres 14, you can also use more comfortable subscripting to update json values, instead of jsonb_set:
UPDATE data
SET scope['sites'] = (
SELECT jsonb_agg(trim(site))
FROM jsonb_array_elements_text(scope['sites']) AS s(site)
);
(online demo)

How to add a column to a table using combined columns from the same table?

I needed basic help on how to combine columns into one new column in the same table. I have done the below as a SELECT command and it works fine. I just don't know how to add it to the table permanently so that it becomes part of the table.
SELECT *, concat(z41, z42, z43, z44) AS option_3,
concat(z411, z412, z413, z421, z422, z423, z431, z432, z433, z434, z444,z443, z442, z441) AS option_4,
concat(z4211, z4212, z4213, z4214, z4215, z4311, z4312, z4313, z4314, z4431, z4432, z4433, z4434, z4421, z4422, z4423, z4424, z4425, z4426) AS option_5
FROM combined_full

Like others have mentioned, you are probably better off using a view. But if you really need this computed data in column then you can do this:
ALTER TABLE combined_full ADD COLUMN option_3 varchar,
ADD COLUMN option_4 varchar,
ADD COLUMN option_5 varchar;
UPDATE combined_full
SET option_3 = concat(z41, z42, z43, z44),
option_4 = concat(z411, z412, z413, z421, z422, z423, z431, z432, z433, z434, z444,z443, z442, z441),
option_5 = concat(z4211, z4212, z4213, z4214, z4215, z4311, z4312, z4313, z4314, z4431, z4432, z4433, z4434, z4421, z4422, z4423, z4424, z4425, z4426);
When adding new rows to the table, you should either also enter values for these three new columns, or create an insert trigger so that the values are automatically calculated as you do above.

"so that it becomes part of the table" - you can't. Unfortunately Postgres (as of 9.6) has no (persisted) computed columns.
If the expression is not very expensive to calculate and you don't need an index on it, I would suggest to create a view that contains the expression.
Given the example in your question, this should be good enough in your case as concatenating values isn't really that expensive.
If you really think you need to persist the calculation of the expression because e.g. you want to create an index on that or you constantly use that expression in a where clause, you will need to add a regular column to the table and a trigger that updates the expression when a row is inserted or updated.

How to insert first character of one column into another column?

I have a table with more than 30.000 entries and have to add a new column (zip_prefixes) containing the first digit of the a zip code (zcta).
I created the column successfully:
alter table zeta add column zip_prefixes text;
Then I tried to put the values in the column with:
update zeta
set zip_prefixes = (
select substr(cast (zctea as text)1,1)
from zeta)
)
Of course I got:
error more than one row returned by a subquery used as an expression
How can I get the first digit of the value from zctea into column zip_prefixes of the same row?

No need for sub-select:
update zeta
set zip_prefixes = substr(zctea, 1, 1);

update zeta
set zip_prefixes = substr(zctea as text)1,1)
There is no need for select query and casting

Consider not adding a functionally dependent column. It's typically cleaner and cheaper overall to retrieve the first character on the fly. If you need a "table", I suggest to add a VIEW.
Why the need to cast(zctea as text)? A zip code should be text to begin with.
Name it zip_prefix, not zip_prefixes.
Use the simpler and cheaper left():
CREATE VIEW zeta_plus AS
SELECT *, left(zctea::text, 1) AS zip_prefix FROM zeta; -- or without cast?
If you need the additional column in the table and the first character is guaranteed to be an ASCII character, consider the data type "char" (with double quotes). 1 byte instead of 2 (on disk) or 5 (in RAM). Details:
What is the overhead for varchar(n)?
Any downsides of using data type "text" for storing strings?
And run both commands in one transaction if you need to minimize lock time and / or avoid a visible column with missing values in the meantime. Faster, too.
BEGIN;
ALTER TABLE zeta ADD COLUMN zip_prefix "char";
UPDATE zeta SET zip_prefixes = left(zctea::text, 1);
COMMIT;

Show all numeric rows or vice-versa postgresql

I have a table named "temp_table" and a column named "temp_column" of type varchar. The problem is "temp_column" must be of type integer. If I will just automatically update the table into type integer, it will generate an error since some data has non-numeric data in it.
I want a query that will show all rows if "temp_column" has non-numeric values in it (or the other way around) and update or SET the value accordingly. I'm having a hard time since ISNUMERIC is not available in postgresql.
how to do this?

This will show all rows where you have non-integer values in that column. It uses a regular expression to find all values that have anything else than just numbers in it:
select *
from temp_table
where temp_column ~ '[^0-9]';
this can also be used in an update statement:
update temp_table
set temp_column = null
where temp_column ~ '[^0-9]';
This will also filter out "numeric" values like 3.14 as those aren't integers.

Alter PostgreSQL column from integer to decimal

Thanks to a last minute client request a integer field in our database now needs to be a decimal, to two points.A value of 23 should become 23.00.
Is there a nice way I can convert the table and cast the data across?
I'll freely admit, I haven't done anything like this with PostgreSQL before so please be gentle with me.

Something like this should work:
alter table t alter column c type decimal(10,2);
Edit:
As #Oli stated in the comments; the first number is the entire length of the number (excluding the point) so the maxval for (10,2) would be 99999999.99

alter table table_name alter column columname type decimal(16,2);
for converting data type from int to decimal. with precession after decimal point 2 values it will come for example 10.285 then it will be 10.23.or in decimal place we can use numeric also it will work.