I am working on a vocable trainer written in python and using a SQLite database.
I have a function where the user can change existing vocables. With the following sqlite syntax I can choose a specific row, in this case row 8 from table Table_1
SELECT * FROM 'Table_1' LIMIT 1 OFFSET '8';
The only way I knwo to update rows is the following:
UPDATE 'Table_1' SET answer='bla' WHERE question='blub';
I do not store the ID number of the vocable in a column, I just store question, answer, phase, next_day. Is it possible to update a sepecific row without using this WHERE question 'blub' syntax but using a syntax like:
UPDATE 'Table_1' SET answer='bla' WHERE LIMIT 1 OFFSET '8';
This one is actually not working, but I guess you know what I mean.
Related
I am new to BigQuery and was wondering if there was a way to search for a specific row, then individually update its columns using a Query. I am very new to database and SQL, and would love some of your help.
Yes you can. Typically this is achieved through data manipulation language (DML). For this specific example you would want use an UPDATE statement.
Documentation on this can be found here:
https://cloud.google.com/bigquery/docs/reference/standard-sql/dml-syntax#update_statement
As a word of caution verify your where clause before you execute to ensure you are targeting the correct rows.
For example:
UPDATE your_table
SET assigned_to_user = 'updated_value' -- the value you want to update to
WHERE -- this is where you define your criteria to narrow down to a subset of rows
criteria_column = 'target_values' -- this is your critera
-- and criteria_column_2 = 'other_value' -- if you need to expand more critiera just use logic operators like `and` or `or`
You can also test out what will be updated by issuing a select statement with the same criteria as your update and seeing which columns come back, for example:
select *
from your_table
WHERE
criteria_column = 'target_values'
When I am trying to update a column with character datatype using update statement. It says 0 rows update and does not throw any error. As the number of columns are much i tried using where clause using specific column out of it...where it updates the row.
Issue is when all the columns are used to alter the value, it gives back 0 rows updated. I have to automate it in vba code/tool so that it could update using all the rows. I identified the columns using which the value is not being updated but there is no error return.
It only says:
0 rows updated.
But what is wrong with that specific column(datatype...decimal).
Please help. I have searched whole internet but no results.
If you are trying to update a specific value in your database and only that one, you may have a rounding issue. This mean the value you see is not the exact value stored.
So you may try to update it with a specific range.
First select what you want to update:
select rowid from table_1
where val_x between <x>-<upsilon> and <x>+<upsilon>;
Update if you have only one value;
update table_1 set val_x = <new_val>
where val_x between <x>-0.001 and <x>+0.001
;
(otherwise, if more than 1 value, decrease <upsilon> to 0.0001, etc.)
Hope it helps
Can I use addition in database?
For example: I have data inside database that is integer. It has a value of 5.
Is there a query that will add another 1 to that? So it will become 6.
Please help me I'm a beginner.
This is the most basic form of an update statement:
update the_table
set the_column = the_column + 1
where the_column = 5;
Note that the above will update all rows where the_colum has the value 5. You most probably want to change the where clause to something different, e.g. by selecting only a single row by using a condition on the primary key column(s) of the table.
Check the manual of your DBMS for details, e.g.: http://www.postgresql.org/docs/current/static/dml-update.html
So I'm trying to get a part of a value from a column and insert that part into another column - new column. BOTH columns are in the same table. So what i want should look something like this:
id newColumn oldColumn
1 12 123 some text
2 24 246 some text
....
I know how to get 12 and 24 using SUBSTR, but how do i enter the data for each row in the table. Should i be using self-join or something else?
First you have to add new col using following command:-
ALTER TABLE TAB_NAME
ADD COLUMN COL_NAME(VARCHAR(10));
After that execute this command:-
UPDAET TAB_NAME
SET COL_NAME = SUBSTRING(OLDCOLUMN, 1, 2);
I think this might help you.
No need to join, it's just a plain UPDATE:
update tablename set newColumn = substring(oldColumn from 1 for 2)
substring is ANSI SQL, some dbms have substr and other versions.
The question is why you are doing this? What do you expect to find in newColumn if someone later updates oldColumn to another value? Maybe you should have a view instead, where newColumn always has up to date values?
Please get into the habit of ALWAYS specifying the DB engine you are using... It helps us to help you - we can provide more relevant answers.
You might want to consider using a calculated column as opposed to storing the information again.
In SQL Server you could do something like this
ALTER TABLE YourTable
ADD new_column as SUBSTRING(old_column, 1, 2);
This way you don't need to insert or update this column it is always consistent with the original column. and you just use it in your select statement in the usual way.
select new_column from YourTable
I'm looking for a possible solution to the following. I have data stored in a table to keep track of a special increment number the customer wants in the DB. This is a special number they use internally.
What I would like to do is automatically increment this number in the table when I select it. So I don't have the problem of another transaction, from someone else using the system, using the same ID number.
So I want to select the current number and increment it by one at once so I don't have duplicates. How would I go about doing this if it is even possible?
UPDATE the_table
SET the_column = the_column + 1
WHERE qualifier = X
RETURNING the_column;
This ought to do the trick, with the caveat that it will return the new id rather than the old one:
UPDATE foo
SET id=nextval('foo_sequence')
WHERE ...
RETURNING *