How do I populate an empty column in my sql database?
I have a list that I want in the last column of my database. If I use executemany it just adds rows on the bottom of my database. Is there a way to fill it from the top? The column is currently populated with NULL values.
Just to be clear. I want the first item in the list to be put in the first row and item n on the list to be put into row n.
Thanks in advance
*Always take backup of your database, just incase you want to revert it back to original state.
Each row in your database table should have a unique primary key. As you mentioned you have a list to be uploaded in the last column, I assume you have some kind of relationship that distinguishes which list item goes to which row in the last column of the table.
You an update a single row by simple update syntax as below:
UPDATE table_name
SET last_column = somevalue_from_list
WHERE id = unique_row_id;
If you want to update all the rows with the same value then
UPDATE table_name
SET last_column = one_value_for_all_rows;
Follow the below suggestion only when you are using phpmyadmin to manage your tables:
If you want to update each row with the unique value from the list then my suggestion will be to export your table in csv format, open in excel like software and add your last column values in last column of each row and then import the changed table back to the database.
Hope this help.
Related
Right now im using Smartsheet API 2.0 were i can update only using a RowID (basically a fixed row number) in a Smartsheet. Instead i need to update using a value from a column which i created.
To update a cell you'll need both the row id and the column id. If you want to set a cell values for all cells created after adding a column you'll need to loop over all existing rows and update each of them.
Concerning performance and best practise, while using update rows you can send a batch of rows.
I have two databases with the same structure. The first is the main one, while the second get updated periodically (in reality I have multiple "secondary" databases that I want to merge one by one into the main one).
The structure of the main and the secondary databases is identical.
I want to periodically dump all new values from the secondary database in the main one. However, the second time I do it, I want to exclude rows that were already copied the first time (and so on).
The tables in all these database have:
an ID column set as PRIMARY KEY going from 1 to N for each database (I suspect this was a mistake, but at the moment I can't change this)
a DATE column, representing a posix timestamp (float)
some other columns
My code looks like this:
ATTACH DATABASE secondary.db AS temp_db
DROP TABLE IF EXISTS my_table_temp
CREATE TABLE my_table_temp AS SELECT * FROM my_table
INSERT INTO main.my_table_temp SELECT * FROM temp_db.my_table
DELETE FROM my_table
INSERT INTO main.my_table SELECT DISTINCT * FROM main.my_table_temp ORDER BY date
DROP TABLE my_table_temp
the problem is that - I suspect due to the repeated ID column - the DISTINCT clause returns me:
UNIQUE constraint failed: my_table.id
However I don't care at all of the ID field that could also be dropped or reset.
NOTES:
the secondary databases are constantly updated by a code that - at the moment - I can't change
I initialize the "main" database copy-pasting one of the secondary to avoid regenerating the whole structure from scratch. Maybe there is a better way of doing this
Apologies if this is a naive question, but I'm very new with SQLite.
Thanks
Following the advice from #forpas, I solved this with the following code:
Assuming the columns to be id,date,col1 and col2
ATTACH DATABASE secondary.db AS temp_db
DROP TABLE IF EXISTS my_table_temp
CREATE TABLE my_table_temp AS SELECT date,col1,col2 FROM my_table
INSERT INTO main.my_table_temp SELECT date,col1,col2 FROM temp_db.my_table
DROP TABLE my_table /* I need to recreate my_table as I've removed a column*/
CREATE TABLE main.my_table AS SELECT DISTINCT date,col1,col2 FROM main.my_table_temp ORDER BY date
DROP TABLE my_table_temp
also, I automatized the extraction of the column names doing
SELECT name FROM PRAGMA_TABLE_INFO('my_table');
This is then passed to the python code running the script and the column id is removed from the list. Note that the second (and following) time I run this code, the column id won't be present in my_table to start with. However this approach allows the code to be the same in the two cases: either if the column id is there or not.
This procedure is then iterated over each table name to fully merge the two databases.
I wanted to insert several lines to database using DBGrid.
on my query, I selected for example:
select * from cust where id='0';
that code will return no record at all so my dbgrid will not show anything but an empty row. Now I wanted to put in data in empty row with new data. However my data needs 2 lines from dbgrid. I wanted dbgrid creates an empty row right after I fill last column in first row. How do I code that? (without inserting the first row data because later I'll insert everything with a seperated button).
thanks!
you can add records in your table with NULLin each column.
For example, suppose the table where the DBGrid is binded to has 4 columns, than you can try this code to add empty records
Query1.InsertRecord([null, null, null, null]);
With this code you can add as many empty records as you like in the DBGrid
That is assuming that the query component you are using supports the InsertRecord method...
I have a table that is actually a ranking list. I want to give user a chance to rearrange that top the way he wants, ergo, allow him to move the rows in that table. Should I create a separate column that would hold the place, or can it be done using embedded order in table?
The documentation says:
If a SELECT statement that returns more than one row does not have an ORDER BY clause, the order in which the rows are returned is undefined.
(This is true for all SQL databases.)
So you cannot rely on the order that the rows happen to be stored in; you have to use some value in some table column.
Ok I have a sqlite db, that has roughly 100 rows. It is kind of a strange thing that I'm trying to do, but I need to insert a new row between each of the existing rows.
I have been trying to use the Insert statement as follows, but haven't had any luck:
insert into t1(column1) values("hello") where id%2 == 0
So I'm basically trying to use the %-operator to tell me if the id is even or odd. For every even id number, I'd like to insert a new row.
What am I missing? What can I do differently? How can I insert a new row into every other row and have the index updated as well?
Thanks
Your question assumes that the rows have some kind of built-in order to them, and that you can insert rows between other rows. That's not true.
It is true that rows have an order on disk, and that the id column is usually assigned in order, but that's an implementation detail. When you perform a query, the database is free to return the rows in any order it chooses, unless you specify what you want with an ORDER BY clause.
Now, I'm assuming what you really want is to insert rows between the existing rows in id order. One way to get what you want would look like this:
UPDATE t1 SET id = id * 2
INSERT INTO t1 (id, column) SELECT id+1, "hello" FROM t1
The UPDATE would double the ids of all the existing rows (so 1,2,3 becomes 2,4,6); then the INSERT would perform a query on t1 and use the result to insert a new set of rows with id values one more than the existing rows (so 2,4,6 becomes 3,5,7).
I haven't tested the above statements, so I don't know if they would work or if they require some extra trickery (like a temporary table) since we are querying and updating the same table in one statement. Also I may have made a syntax error.
Don't consider the rows as pre-ordered in the database. A database will store them as they come in, or according to an index. It's your task to order them on retrieval (i.e. when you query for data) according to your needs.