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How do I make a list of data frames?
... data import function for read.csv as appropriate. readr::read_csv or data.table::fread will be faster, or you may also need a different function for a different file type.
Either way, it's handy to name the list elements to match the files
names(my_data) <- gsub("\\.csv$", "", my_files)
# or, ...
Design Pattern for Undo Engine
...e object is needed, you lookup the current definition of the object from a table. The table contains a linked list for each object that contains all the previous versions, along with information regarding which checkpoint they were active for.
Implementing undo/redo is simple: Do your action and es...
How to grant remote access permissions to mysql server for user?
...FIED BY 'YOUR_PASS'
WITH GRANT OPTION;
FLUSH PRIVILEGES;
*.* = DB.TABLE you can restrict user to specific database and specific table.
'root'@'%' you can change root with any user you created and % is to allow all IP. You can restrict it by changing %.168.1.1 etc too.
If that doesn't ...
SQLite string contains other string query
...
Using LIKE:
SELECT *
FROM TABLE
WHERE column LIKE '%cats%' --case-insensitive
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SQL Server: Get data for only the past year
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This will have very bad performance on big tables, you query will loop over every record to evaluate the year value of the date, it would be better to use a date range
– Adriaan Davel
May 30 '12 at 15:43
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Working copy XXX locked and cleanup failed in SVN
...deleting a record in the SQLite ".svn\wc" file lock record in the WC_LOCK table.
I opened the "WC" file with SQLite editor and executed
delete from WC_LOCK
Following eakkas's comment, you might need to delete all the entries from WORK_QUEUE table as well.
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Why use a READ UNCOMMITTED isolation level?
... sense for reading data will never be modified. Trying to use that to read tables that would be written to means that you will in practice read something that gets rolled back. It's not just that you are reading data that's a few seconds old, but you ....................................................
How to get last N records with activerecord?
...rails is lazy, it will eventually hit the database with SQL like: "SELECT table.* FROM table ORDER BY table.id DESC LIMIT 5".
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What are the use cases of Graph-based Databases (http://neo4j.org/)? [closed]
...nto the current blub architecture, use a graph database, or CouchDB, or BigTable, or whatever fits your app and you think is cool. It might give you an advantage, and its fun to try new things.
Whatever you chose, try not to build the database engine yourself unless you really like building databas...
Difference between HashSet and HashMap?
... functions. This is critical because HashMap uses power-of two length hash tables." weblogs.java.net/blog/2005/06/18/hashmap-implementation - however, if you look at the doc you'll see that this hash distributes things over "buckets", so in the end I believe two things can get mapped the same bucket...