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How can you represent inheritance in a database?
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Does other DBs support INHERITS besides PostgreSQL ? MySQL for example ?
– giannis christofakis
Mar 11 '16 at 9:00
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Difference between natural join and inner join
... definition of a natural join is to join on *all like-named columns*. From MySQL doc: The NATURAL [LEFT] JOIN of two tables is defined to be semantically equivalent to an INNER JOIN or a LEFT JOIN with a USING clause that names all columns that exist in both tables.. And another thing - in practice ...
SQL Server: SELECT only the rows with MAX(DATE)
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For MySql you can do something like the following:
select OrderNO, PartCode, Quantity from table a
join (select ID, MAX(DateEntered) from table group by OrderNO) b on a.ID = b.ID
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When to use SELECT … FOR UPDATE?
...ends on the concurrency control your database system is using.
MyISAM in MySQL (and several other old systems) does lock the whole table for the duration of a query.
In SQL Server, SELECT queries place shared locks on the records / pages / tables they have examined, while DML queries place update ...
What does “Document-oriented” vs. Key-Value mean when talking about MongoDB vs Cassandra?
... of a database at the top level, then collections which are like tables in MySQL (for example) and then documents which are contained within the collection, like rows in MySQL. Each document has a field and a value where this is similar to columns and values in MySQL. Fields can be simple key / valu...
How can prepared statements protect from SQL injection attacks?
...ven alter it, as every SQL injection example shows it (all examples in PHP/Mysql):
$expected_data = 1;
$query = "SELECT * FROM users where id=$expected_data";
will produce a regular query
SELECT * FROM users where id=1
while this code
$spoiled_data = "1; DROP TABLE users;"
$query = "S...
SQL statement to select all rows from previous day
...microsoft.com/en-us/library/ms189794.aspx) the question you link to is for MySql, which I guess works differently as you have found. You will find that SQL is not completely interchangeable, there are many differences like this between different vendors, especially regarding date handling.
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Django-Admin: CharField as TextArea
...form = BookForm
admin.site.register(Book, BookAdmin)
If you are using a MySQL DB, your column length will usually be autoset to 250 characters, so you will want to run an ALTER TABLE to change the length in you MySQL DB, so that you can take advantage of the new larger Textarea that you have in y...
PHP Warning: POST Content-Length of 8978294 bytes exceeds the limit of 8388608 bytes in Unknown on l
...oad-max-filesize (change 2M to 2000M).
3. Now stop the Apache server and MySQL.
4. Now restart Apache server and MySQL.
It worked fine after that.
Enjoy ur working now :)
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Django CharField vs TextField
...nce among these three types", but AFAIK there are some differences in e.g. MySQL, so this is something to keep in mind.
A good rule of thumb is that you use CharField when you need to limit the maximum length, TextField otherwise.
This is not really Django-specific, also.
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