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How to UPSERT (MERGE, INSERT … ON DUPLICATE UPDATE) in PostgreSQL?
...ions:
Individual insert/update operations in a retry loop; or
Locking the table and doing batch merge
Individual row retry loop
Using individual row upserts in a retry loop is the reasonable option if you want many connections concurrently trying to perform inserts.
The PostgreSQL documentation co...
Set cellpadding and cellspacing in CSS?
In an HTML table, the cellpadding and cellspacing can be set like this:
28 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?
...
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...
Is ASCII code 7-bit or 8-bit?
...
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...
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...
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
...
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...