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Extract a dplyr tbl column as a vector
...yr tbl as a vector, from a tbl with database back-end (i.e. the data frame/table can't be subset directly)?
7 Answers
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Postgres unique constraint vs index
... but important issue, so I decided to learn by example.
Let's create test table master with two columns, con_id with unique constraint and ind_id indexed by unique index.
create table master (
con_id integer unique,
ind_id integer
);
create unique index master_unique_idx on master (ind_id)...
Space between two rows in a table?
...ements with the class spaceUnder. This will make it possible to use nested tables. (Cell C and D in the example code.) I'm not too sure about browser support for the direct child selector (think IE 6), but it shouldn't break the code in any modern browsers.
/* Apply padding to td elements that ...
Check for changes to an SQL Server table?
How can I monitor an SQL Server database for changes to a table without using triggers or modifying the structure of the database in any way? My preferred programming environment is .NET and C#.
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How to see indexes for a database or table in MySQL?
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To see the index for a specific table use SHOW INDEX:
SHOW INDEX FROM yourtable;
To see indexes for all tables within a specific schema you can use the STATISTICS table from INFORMATION_SCHEMA:
SELECT DISTINCT
TABLE_NAME,
INDEX_NAME
FROM INFORM...
What is a plain English explanation of “Big O” notation?
...billion operations per second).
If we use a simple structure called a hash table (an instant-speed lookup table, also known as a hashmap or dictionary), we pay a small cost by preprocessing everything in O(N) time. Thereafter, it only takes constant time on average to look up something by its key (i...
Is ASCII code 7-bit or 8-bit?
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The original ASCII table is encoded on 7 bits therefore it has 128 characters.
Nowadays most readers/editors use an "extended" ASCII table (from ISO 8859-1), which is encoded on 8 bits and enjoys 256 characters (including Á, Ä, Œ, é, è an...
Implementing Comments and Likes in database
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The most extensible solution is to have just one "base" table (connected to "likes", tags and comments), and "inherit" all other tables from it. Adding a new kind of entity involves just adding a new "inherited" table - it then automatically plugs into the whole like/tag/comment m...
Get size of all tables in database
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SELECT
t.NAME AS TableName,
s.Name AS SchemaName,
p.rows,
SUM(a.total_pages) * 8 AS TotalSpaceKB,
CAST(ROUND(((SUM(a.total_pages) * 8) / 1024.00), 2) AS NUMERIC(36, 2)) AS TotalSpaceMB,
SUM(a.used_pages) * 8 AS UsedSpaceK...
Colspan all columns
... td tag should span all columns (when the exact amount of columns in the table will be variable/difficult to determine when the HTML is being rendered)? w3schools mentions you can use colspan="0" , but it doesn't say exactly what browsers support that value (IE 6 is in our list to support).
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