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How to delete a column from a table in MySQL
Given the table created using:
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select and update database record with a single queryset
...ew value based on the old field value that is do something like:
update my_table set field_1 = field_1 + 1 where pk_field = some_value
use query expressions:
MyModel.objects.filter(pk=some_value).update(field1=F('field1') + 1)
This will execute update atomically that is using one update request to...
Is there any difference between the `:key => “value”` and `key: “value”` hash notations?
...strings. Although hash-rockets provide freedom and functionality for hash-tables, specifically allowing strings as keys, application performance may be slower than if the hash-tables were to be constructed with symbols as hash-keys. The following resources may be able to clarify any differences be...
ORA-00979 not a group by expression
...ave a database like this:
FOO BAR
0 A
0 B
and you run SELECT * FROM table GROUP BY foo. This means the database must return a single row as result with the first column 0 to fulfill the GROUP BY but there are now two values of bar to chose from. Which result would you expect - A or B? Or shou...
Getting key with maximum value in dictionary?
...th item>
Returned values will be compared.
Dict
Python dict is a hash table. A key of dict is a hash of an object declared as a key. Due to performance reasons iteration though a dict implemented as iteration through it's keys.
Therefore we can use it to rid operation of obtaining a keys list.
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Why does PostgreSQL perform sequential scan on indexed column?
Very simple example - one table, one index, one query:
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How Do I Get the Query Builder to Output Its Raw SQL Query as a String?
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Use the toSql() method on a QueryBuilder instance.
DB::table('users')->toSql() would return:
select * from `users`
This is easier than wiring up an event listener, and also lets you check what the query will actually look like at any point while you're building it.
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Use variable with TOP in select statement in SQL Server without making it dynamic [duplicate]
...'s possible to use a variable in the top clause.
select top (@top) * from tablename
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Using DISTINCT and COUNT together in a MySQL Query
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use
SELECT COUNT(DISTINCT productId) from table_name WHERE keyword='$keyword'
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In Django, how does one filter a QuerySet with dynamic field lookups?
... right. It sounds like the "field" is actually a key to a row in another table, not a column.
Specific filter buttons. Wait... That's the way the Django admin works. Specific filters are turned into buttons. And the same analysis as above applies. A few filters make sense. A large number of ...