大约有 22,000 项符合查询结果（耗时：0.0322秒） [XML]
SQL - many-to-many table primary key
... index, on (col1, col2) also handles the 'both' case). The downside is the extra storage needed for the extra column. This is usually not significant, so the advice is far from awful. Nevertheless, if col1 and col2 are big or of very different sizes, you can save yourself some space without hurting ...
Combine two or more columns in a dataframe into a new column with a new name
...t for example is like: A - B instead of A-B. Is it possible to remove this extra space?
– Chetan Arvind Patil
Oct 6 '17 at 2:35
9
...
Check if a program exists from a Makefile
...= $(foreach exec,$(EXECUTABLES),\
$(if $(shell which $(exec)),some string,$(error "No $(exec) in PATH")))
Note the use of the := assignment operator that is required in order to force immediate evaluation of the RHS expression. If your Makefile changes the PATH, then instead of the last li...
How to efficiently count the number of keys/properties of an object in JavaScript?
...).length worked best for me, because my return object is sometimes a plain string with no properties within it. _.size(obj) gives me back the length of the string, while _.keys(obj).length returns 0.
– Jacob Stamm
Nov 23 '15 at 23:02
...
How do I horizontally center an absolute positioned element inside a 100% width div? [duplicate]
...ent. Now magic happens when margin is set to auto. margin takes up all the extra space(equally on each side) leaving the content to its specified width. This results in content becoming center aligned.
share
|
...
How do I Sort a Multidimensional Array in PHP [duplicate]
...set contains columns that cannot be compared in a "dumb" manner (e.g. date strings) you can also specify how to convert these items to a value that can be directly compared (e.g. a DateTime instance).
It's associative if you want: this code takes care of sorting items, but you select the actual sort...
node.js database [closed]
...
By default, node_redis will return JavaScript strings for all commands. To get buffers instead, create a client with createClient(port, host, { return_buffers: true });
– Matt Ranney
Sep 20 '11 at 6:40
...
How to change colors of a Drawable in Android?
...
If you want to use a color resource rather than a string (#ff0000 etc), you can use e.g. int iColor = getResources().getColor(R.color.primary)
– Ben Clayton
Aug 20 '14 at 15:02
...
Is using Random and OrderBy a good shuffle algorithm?
...Or you could replace the > 0 with >= 0 and not have to (although, an extra RNG hit plus a redundant assignment)
– FryGuy
Nov 29 '09 at 20:40
4
...
Rails: Is there a rails trick to adding commas to large numbers?
...
Sure, it reverses the string, then adds a comma after any sequence of 3 digits that is also followed by another digit, then reverses it back.
– pguardiario
Feb 22 '13 at 0:04
...