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Fastest way to replace NAs in a large data.table
I have a large data.table , with many missing values scattered throughout its ~200k rows and 200 columns. I would like to re code those NA values to zeros as efficiently as possible.
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jquery UI Sortable with table and tr width
I am using jQuery UI sortable to make my table grid sortable. The code seems to work fine but because I am not adding width to td s, when I drag the tr it shrinks the content.
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How do I drop a foreign key constraint only if it exists in sql server?
I can drop a table if it exists using the following code but do not know how to do the same with a constraint:
10 Answers
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How do I find a “gap” in running counter with SQL?
I'd like to find the first "gap" in a counter column in an SQL table. For example, if there are values 1,2,4 and 5 I'd like to find out 3.
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Return number of rows affected by UPDATE statements
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CREATE PROCEDURE UpdateTables
AS
BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;
DECLARE @RowCount1 INTEGER
DECLARE @RowCount2 INTEGER
DECLARE @RowCount3...
Changing the maximum length of a varchar column?
...characters to 500 without losing the contents. I've dropped and re-created tables before but I've never been exposed to the alter statement which is what I believe I need to use to do this. I found the documentation here: ALTER TABLE (Transfact-SQL) however I can't make heads or tails of it.
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Removing duplicate rows from table in Oracle
I'm testing something in Oracle and populated a table with some sample data, but in the process I accidentally loaded duplicate records, so now I can't create a primary key using some of the columns.
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Rails has_and_belongs_to_many migration
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You need to add a separate join table with only a restaurant_id and user_id (no primary key), in alphabetical order.
First run your migrations, then edit the generated migration file.
Rails 3
rails g migration create_restaurants_users_table
Rails 4:
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List columns with indexes in PostgreSQL
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Create some test data...
create table test (a int, b int, c int, constraint pk_test primary key(a, b));
create table test2 (a int, b int, c int, constraint uk_test2 unique (b, c));
create table test3 (a int, b int, c int, constraint uk_test3b unique (b), co...
What are the differences between a clustered and a non-clustered index?
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Clustered Index
Only one per table
Faster to read than non clustered as data is physically stored in index order
Non Clustered Index
Can be used many times per table
Quicker for insert and update operations than a clustered index
Both types of inde...