I want to retrieve the last 2 rows inserted into an SQLite database for display in a label. What would be the proper SQLite statement to retrieve these rows?
If you last inserted data has just inserted (maybe in the same method), you can use:
last_insert_rowid
If you like to read the last insert data after, let's say a app re/start, then you need to do some ordering.
If you have a auto-incrementing id row, you can do the following
"SELECT * from your_table ORDER BY your_autoinc_id DESC LIMIT 2"
Related
How do I insert a row between here?
Data is not intended to be stored SQL tables in any particular order, so it's not appropriate to insert a row at a particular position. You use an SQL SELECT query to extract the data you want and ORDER BY to specify how it is sorted. If you really want to have this row in a particular position, add an ID column as the primary key and number the ID column values in the sequence that you want. Whatever you are using to view your rows will order them by the ID column by default. However, you're going to experience this same problem every time you want to add a new row as SQL tables are not intended to be used in this way.
I have this fairly large DB. It contains lots of column. One of the will have a value that I need to select, but the DB has several of that value. How can I insert into a column in the row thats the newest in the DB, with a matching column.
Without knowing the ins and outs of your database, I think you would likely want to select the largest id you have in the auto incrementing row. For instance:
SELECT MAX(UNIQUE_ID) FROM TABLE WHERE MATCHING_COLUMN = MATCHING_VALUE
From there you can take your unique ID and insert into that row.
I have a table that has no indexed rows, nor a specific column...
Let's say "City, PersonName, PersonAge". I need to obtain the last 5 people inserted in that table...
How can I do it in in DB2?
I tried
select * from PEOPLE fetch first 5 rows only
this work perfectly... but no idea how to do it with the LAST rows....
You can't select the last 5 rows inserted, the database doesn't keep track of this. You need some sort of autoincremented ID or timestamp and order by that column descending.
i have 10 rows of data in my table. now i want to insert a row of data just after the 9th data and before row 10..if am not mistaken ,in mysql db this thing is possible before there's a before and after clause, how bout in oracle ?
here's my starting insert statement, let's say i want to insert it after the 9th data ,how?
INSERT INTO MYTABLE (TITLE,DESCRIPTION,STATUS) VALUES ('blahblah','descriptionblah',1);
There is no inherrent order to rows in a table, and there is no guarantee a particular ordering will be preserved between selects. Consider adding a column containing the required ordering and when querying the table, order the result set by that column.
To insert a row which should appear at a particular position in the result set, ensure that the value you place in the ordering column is appropriate.
I have a table with 4 columns. The first column is unique for each row, but it's a string (URL format).
I want to update my table, but instead of using "WHERE", I want to update the rows in order.
The first query will update the first row, the second query updates the second row and so on.
What's the SQL code for that? I'm using Sqlite.
Edit: My table schema
CREATE table (
url varchar(150),
views int(5),
clicks int(5)
)
Edit2: What I'm doing right now is a loop of SQL queries
update table set views = 5, click = 10 where url = "http://someurl.com";
There is around 4 million records in the database. It's taking around 16 seconds in my server to make the update. Since the loop update the row in order, so the first query update the first row; I'm thinking if updating the rows in order could be faster than using the WHERE clause which needs to browse 4 million rows.
You can't do what you want without using WHERE as this is the only way to select rows from a table for reading, updating or deleting. So you will want to use:
UPDATE table SET url = ... WHERE url = '<whatever>'
HOWEVER... SqlLite has an extra feature - the autogenerated column, ROWID. You can use this column in queries. You don't see this data by default, so if you want the data within it you need to explicitly request it, e.g:
SELECT ROWID, * FROM table
What this means is that you may be able to do what you want referencing this column directly:
UPDATE table SET url = ... WHERE ROWID = 1
you still need to use the WHERE clause, but this allows you to access the rows in insert order without doing anything else.
CAVEAT
ROWID effectively stores the INSERT order of the rows. If you delete rows from the table, the ROWIDs for remaining rows will NOT change - hence it is possible to have gaps in the ROWID sequence. This is by design and there is no workaround short of re-creating the table and re-populating the data.
PORTABILITY
Note that this only applies to SQLite - you may not be able to do the same thing with other SQL engines should you ever need to port this. It would be MUCH better to add an EXPLICIT auto-number column (aka an IDENTITY field) that you can use and manage.