大约有 47,000 项符合查询结果（耗时：0.0330秒） [XML]
Select rows which are not present in other table
...task, all of them standard SQL.
NOT EXISTS
Often fastest in Postgres.
SELECT ip
FROM login_log l
WHERE NOT EXISTS (
SELECT -- SELECT list mostly irrelevant; can just be empty in Postgres
FROM ip_location
WHERE ip = l.ip
);
Also consider:
What is easier to read in EXISTS...
What's faster, SELECT DISTINCT or GROUP BY in MySQL?
...'t, then use DISTINCT.
GROUP BY in MySQL sorts results. You can even do:
SELECT u.profession FROM users u GROUP BY u.profession DESC
and get your professions sorted in DESC order.
DISTINCT creates a temporary table and uses it for storing duplicates. GROUP BY does the same, but sortes the disti...
MySQL: Fastest way to count number of rows
...s.
The solution is SQL_CALC_FOUND_ROWS. This is usually used when you are selecting rows but still need to know the total row count (for example, for paging).
When you select data rows, just append the SQL_CALC_FOUND_ROWS keyword after SELECT:
SELECT SQL_CALC_FOUND_ROWS [needed fields or *] FROM t...
JOIN two SELECT statement results
Is it possible to join the results of 2 sql SELECT statements in one statement?
I have a database of tasks where each record is a separate task, with deadlines (and a PALT , which is just an INT of days from start to deadline. Age is also an INT number of days.)
...
What are five things you hate about your favorite language? [closed]
...ly typed, compared to, say, Python (e.g. you can assign integers to chars, cast anything to anything via void* pointers, etc.) It is statically typed instead of dynamically typed, and also requires explicit typing instead of type inference, but those are unrelated to strong v/s weak typing. [Random ...
Encode html entities in javascript
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@S.B. Thanks for that note, I even got to cast the final approve vote :)
– Chris Baker
Apr 8 '14 at 14:21
1
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How would one write object-oriented code in C? [closed]
...; // This is a non-virtual call
Stack.push(st, thing1); // This is like casting *st to a Stack (which it already is) and doing the push
st->my_type.push(st, thing2); // This is a virtual call
}
I didn't do the destructor or delete, but it follows the same pattern.
this_is_here_as_an_exam...
Why are C# interface methods not declared abstract or virtual?
...he class' v-table, each slot has a pointer to one of the virtual methods. Casting an object to an interface type generates a pointer to the section of the table that implements the interface methods. The client code that uses the interface reference now sees the first interface method pointer at o...
Search for selection in vim
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Check this Vim tip: Search for visually selected text
Or you can simply yank the selected text with y and go to search mode /, then you can paste the last yanked text with Ctrl+R 0
share
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What is the printf format specifier for bool?
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The cast is not needed.
– user529758
Jun 25 '13 at 20:52
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