大约有 43,000 项符合查询结果（耗时：0.0542秒） [XML]
ALTER TABLE to add a composite primary key
...dexed from left to right.
For example, consider the following queries:
A) SELECT person, place, thing FROM provider WHERE person = 'foo' AND thing = 'bar';
B) SELECT person, place, thing FROM provider WHERE person = 'foo' AND place = 'baz';
C) SELECT person, place, thing FROM provider WHERE person ...
How to find the size of an array in postgresql
...ikely) and are running PostgreSQL 9.4 or higher, you can use cardinality:
SELECT cardinality(id) FROM example;
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Missing Push Notification Entitlement
...from the answer given by @Vaiden, in Xcode 8 you can resolve this issue by selecting the target and clicking the "Fix issue". Of course, you'll still need to set up push notifications in the Apple Developer portal (you can simplify the process a little by using the new "Automatically manage signing"...
Difference between JOIN and INNER JOIN
...nal,
or you can specify CROSS JOIN.
OR
For an inner join, the syntax is:
SELECT ...
FROM TableA
[INNER] JOIN TableB
(in other words, the "INNER" keyword is optional - results are the same
with or without it)
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How many database indexes is too many?
...
It depends on the operations that occur on the table.
If there's lots of SELECTs and very few changes, index all you like.... these will (potentially) speed the SELECT statements up.
If the table is heavily hit by UPDATEs, INSERTs + DELETEs ... these will be very slow with lots of indexes since t...
What's the difference between streams and datagrams in network programming?
...ets
stream (TCP, order and delivery guaranteed,no duplication,no length or char boundaries for data,connection-oriented,reliable, concurrency)
datagram(UDP,packet-based, connectionless, datagram size limit, data can be lost or duplicated, order not guaranteed,not reliable)
raw (direct access to lowe...
What's the best way to make a d3.js visualisation layout responsive?
...n the window resizes like so:
var aspect = width / height,
chart = d3.select('#chart');
d3.select(window)
.on("resize", function() {
var targetWidth = chart.node().getBoundingClientRect().width;
chart.attr("width", targetWidth);
chart.attr("height", targetWidth / aspect);
});
...
How to disable typing special characters when pressing option key in Mac OS X? [closed]
...work on MacOSX 10.7+ with IntelliJ Idea, Php/WebStorm, NetBeans, Eclipse.
Select "Set blank for option key" radio in the form, submit the form, and download a patched keyboard layout with "option" key feature disabled. I'm sharing the working file for standard US English keyboard layout:
MacOS &l...
Removing App ID from Developer Connection
...ifiers > App IDs"
Find the app id you wish to delete, highlight it and select "Settings". At the bottom of the resulting screen there is a "Delete" button.
Previously the only way to do this was to use a Safari & Chrome extension written by Simon Whitaker
app-id-sanity downloads
It giv...
How to resume Fragment from BackStack if exists
...teName);
ft.commit();
}
}
The conditional was changed a bit since selecting the same fragment while it was visible also caused duplicate entries.
Implementation:
I highly suggest not taking the the updated replaceFragment() method apart like you did in your code. All the logic is containe...