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',
Related
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;
I'm quite new to scripts and need some help on creating a script doing multiple actions in sequence.
Let's use this tentative (and bisarre) table to illustrate the solution. The table could potentially hold hundreds of entries:
I want to add a PhoneNumber column with varchar type and populate it from the existing PhoneNumber column.
For phone numbers consiting of 5 digits I want to add a leading zero (0) so all entries have the same length (6).
When this is done for all occurances of 5-digit phone numbers I want to delete the old PhoneNumber column
This is how the table should look after step 1:
And after step 2 it should look like this:
Finally, after the third step I want this outcome:
Can this be accomplished with a script? I don't really need the script to follow this exact sequence as long as it results in the desired outcome. This is just the sequence of actions I have thought could be an allright approach.
Here you go
Remember, you can't have 2 columns called the same
ALTER TABLE [TABLENAME] ADD PHONENUMBERCHAR char(6); --Adds a new column
GO;
UPDATE [TABLENAME] SET PHONENUMBERCHAR = RIGHT(CONCAT('000000', PHONENUMBER), 6); --Updates the value
GO;
ALTER TABLE [TABLENAME] DROP COLUMN PHONENUMBER --Deletes the old column
If the value is really an integer, you can use format():
select id, phonenumber, format(phonenumber, '000000')
from t;
You may want to add this as a computed column:
alter table t add phonenumber_6 as (format(phonenumber, '000000'));
select name into viewtable from stdinfo5
My error is:
There is already an object named 'viewtable' in the database.
Can someone explain: I want column with data (adding) into viewtable from the stdinfo5 table.
Thanks!
select ... into SomeTarget from SomeSource will create a physical table with the name SomeTarget!
You can use DROP TABLE SomeTarget to delete this table (carefull with real data!!!) or, what might be better, use select ... into #SomeTarget ....
The # before the name will create this table as temp table which is deleted automatically when it gets out of scope.
In your case it seems, that you do not want to delete the table, but you just want to add one more column. In this case you'd need something like ALTER TABLE viewtable ADD TheColumnName TheColumnType; and then use an UPDATE statement to fill this column. If possible, it was easier to delete the table and re-create it with the missing column...
I would like to be able to add columns to a table with cells who's values are computed by need at 'querytime' when (possibly) selecting over them.
Are there some established ways of doing this?
EDIT: Okay I can do without the 'add columns'. What I want is to make a select query which searches some (if they exist) rows with all needed values computed (some function) and also fills in some of the rows which does not have all needed values computed. So each query would do it's part in extending the data a bit.
(Some columns would start out as null values or similar)
I guess I'll do the extending part first and the query after
You use select expression, especially if you don't plan to store the calculation results, or they are dependant on more than one table. An example, as simple as it could be:
SELECT id, (id+1) as next_id FROM table;
What type of database are you asking for? If it is SQL Server then you can use the computed columns by using the AS syntax.
Eg:
create table Test
(
Id int identity(1,1),
col1 varchar(2) default 'NO',
col2 as col1 + ' - Why?'
)
go
insert into Test
default values
go
select * from Test
drop table Test
In the SQL world it's usually expensive to add a column to an existing table so I'd advise against it. Maybe you can manage with something like this:
SELECT OrderID,
ProductID,
UnitPrice*Quantity AS "Regular Price",
UnitPrice*Quantity-UnitPrice*Quantity*Discount AS "Price After Discount"
FROM order_details;
If you really insist on adding a new column, you could go for something like (not tested):
ALTER TABLE order_details ADD column_name datatype
UPDATE order_details SET column_name = UnitPrice+1
You basically ALTER TABLE to add the new column, then perform an UPDATE operation on all the table to set the value of the newly added column.
I would like to increase all ids in my table by 1000 cause I need to insert there data from other table with excactly the same ids. What is the best way to do that?
update dbo.table set id = id + 1000
go
The best way to go is to not do that. You have to change all related records as well and if you are using identities it gets even more complicated. If you do anything wrong you will seriousl mess up your data integrity. I would suggest that the data you want to insert is the data that needs to have the values changed and if you need to relate back to the data in another tbale, store the original ID in a new field in the table called something like table2id or database2id. If you can't change the existing table, then you can use a lookup table that has both the old id value and the new one.
Under no circumstances should you attempt something of this nature without taking a backup first.
First as HLGEM it seems to be a bad id (think about your foreign keys on id's you must add 1000 to them to).
Second dbo.table has become sys.tables in Server 2008.
Finally you'll need to find the foreign keys columns with this request :
SELECT name,OBJECT_NAME(object_id)
FROM sys.columns
WHERE name like '%id' or name like 'id%'
--depends on where is 'id' in your columns names
name : the column name, OBJECT_NAME : the table name
And update the whole thing (with a tricky request that should looks like this one, but i didn't test with the "update" command) :
CREATE TABLE #TablesWithIds (
columnName varchar(100),
tableName varchar(100)
)
Insert into #TablesWithIds
SELECT name as columnName,OBJECT_NAME(object_id) as tableName
FROM sys.columns
WHERE name like '%id%'
update #TablesWithIds.tableName set #TablesWithIds.columnName = #TablesWithIds.columnName +1000
drop table #TablesWithIds