I found the similar question and solution for the SQL server. I want to replace all my null values with zero or empty strings. I can not use the update statement because my table has 255 columns and using the update for all columns will consume lots of time.
Can anyone suggest to me, how to update all the null values from all columns at once in PostgreSQL?
If you want to replace the data on the fly while selecting the rows you need:
SELECT COALESCE(maybe_null_column, 0)
If you want the change to be saved on the table you need to use an UPDATE. If you have a lot of rows you can use a tool like pg-batch
You can also create a new table and then swap the old one and the new one:
# Create new table with updated values
CREATE TABLE new_table AS
SELECT COALESCE(maybe_null_column, 0), COALESCE(maybe_null_column2, '')
FROM my_table;
# Swap table
ALTER TABLE my_table RENAME TO obsolete_table;
ALTER TABLE new_table RENAME TO my_table;
Related
We have table like :
mytable (pid, string_value, int_value)
This table has more than 20M rows in total. Now we have a feature try to mark all the rows from this tables as invalid. So we need update the table columns: string_Value = NULL and int_value = 0 which indicate this is invalid row ( we still want to keep the pid as it is important to us)
So what is the best way?
I use the following SQL:
UPDATE Mytable
SET string_value = NULL,
int_value = 0;
but this query takes more than 4 minutes in my test env. Is there any better way we can improve it?
Updating all the rows can be quite expensive. Often, it is faster to empty the table and reload it.
In generic SQL this looks like:
create table mytable_temp as
select pid
from mytable;
truncate table mytable; -- back it up first!
insert into mytable (pid, string_value, int_value)
select pid, null, 0
from mytable_temp;
The creation of the temporary table may use different syntax, depending on our database.
Updates can take time to complete. Another way of achieving this is to follow the following steps:
Add new columns with the values you need set as the default value
Drop the original columns
Rename the new columns with the names of the original columns.
You can then drop the default values on the new columns.
This needs to be tested as different DBMSs allow different levels of table alters (i.e. not all DMBSs allow a drop default or a drop column).
I have a large table with given number of rows in which I'd like to replace personal informations with dummy data. I've written functions for this but actually struggling with how to implement it.
I'd like to do something like:
ALTER TABLE SomeTable DROP COLUMN SomeName
ALTER TABLE SomeTable ADD COLUMN SomeName NVARCHAR(30) DEFAULT (SELECT * FROM dbo.FakeName)
Help would be appreciated.
Instead of dropping and adding a column, just do an UPDATE.
If you just want to update the actual data with dummy data , why can't you use update statement as below. We do almost similar in our day to day work. For ex. if we would like to sanitize actual email address of users while restoring the data in my local or test machine (in column SomeName) and in another column we just want to update it with 'XXX' .
UPDATE SomeTable
SET Email_address= SUBSTRING(Email_address,0,CHARINDEX('#',Email_address)) + '#mytest.com',
SomeName2= 'XXX',
I'm using PL/pgSQL and I'm trying to append some rows to a table, or if the table doesn't exist yet I want to create it and append the rows.
Is there some built-in syntax for that?
You can use CREATE TABLE IF NOT EXISTS name (definition) before you INSERT data to it.
I have a "source data" table with columns A,B,C,D,E,F
I use this table to populate a live table by using
INSERT INTO LIVETABLE
SELECT *
FROM SOURCEDATATABLE
Recently, a new column (C1) was added to the LIVETABLE
All I want to do is insert a C1 column into my SOURCEDATATABLE between C and D so that it now is A,B,C,C1,D,E,F. There is no need to populate with data as the LIVETABLE accepts NULLs
Is there any easy solution?
EDIT - MISSING INFORMATION
This table is one of many and my approach to using the INSERT INTO is due to having to use dynamic SQL (for various other reasons) so I cannot specify the column names
There is a reason for the Mantra "I shall not use SELECT *" and you ran straight into it. Add the column to SOURCEDATATABLE (if necessary) and enumerate the columns in the SELECT clause using NULL for the new one.
The only way to insert a new column between two columns is to create a new table with the columns in the order you want, copy the data into it, drop the old table and rename the new table with the old name. Make sure you remove primary key identities to maintain the identity column.
I have a sql statement to insert data into a table for archiving, but I need a merge statement to run on a monthyl basis to update the new table(2) with any data that changed in the old table(1) that should now be moved into archive.
Part of the issue is to remove the moved data from the old table. My insert is not doing that, but I need to have it to where the saved data is purged from the original table.
Is there a single sql statement that will move data out of one table into another in this way? Or does it need to be a two step operation?
the initial statement moved data depending on age and a few other relative factors.
insert is:
INSERT /*+ append */
INTO tab1
SELECT *
FROM tab2
WHERE (Postingdate < TO_DATE ('2001/07/01', 'yyyy/mm/dd')
OR jobname IS NULL)
AND STATUS <> '45';
All help appreciated...
The merge statement will let you do this in one statement by adding a delete statement in the update clause. See Oracle Documentation on Merge.
I think you should try this with a partition table. My idea is to create table which have range partition on date:
create table(id number primary key,name varchar,J_date date )
partition by range(J_date)(PARTITION one_mnth VALUES LESS THAN(sysdate-30)),
partition by range(J_date)(PARTITION one_mnth VALUES LESS THAN(maxvalue)));
then move that partition in to another table and and truncate that partition