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MySQL select where column is not empty
In MySQL, can I select columns only where something exists?
13 Answers
13
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What uses are there for “placement new”?
..._b, ...);
Now you can cluster objects together in a single memory arena, select an allocator which is very fast but does no deallocation, use memory mapping, and any other semantic you wish to impose by choosing the pool and passing it as an argument to an object's placement new operator.
...
Why the switch statement cannot be applied on strings?
...however this might not be so easy for strings (considering run-time locale selection and so on). I suppose that such a thing would have to require constexpr cases, or add in unspecified behaviour (never a thing that we want to do).
– M.M
Jun 11 '15 at 23:37
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How do I sort unicode strings alphabetically in Python?
...just wanted to point out one coding inefficiency in Human Sort. To apply a selective char-by-char translation to a unicode string s, it uses the code:
spec_dict = {'Å':'A', 'Ä':'A'}
def spec_order(s):
return ''.join([spec_dict.get(ch, ch) for ch in s])
Python has a much better, faster and ...
30岁之后，程序员该向什么方向发展？ - 杂谈 - 清泛网 - 专注C/C++及内核技术
...ools，用得人比较少。有一次我在Github上找到一个mootools的插件，很久没维护了。但是使用过程中发现一些问题，反复测试确认后，怀着忐忑的心情，我向原地址提交了commit，没想到他很快就合并了，并且向我表示感谢。当时的心...
SQL: capitalize first letter only [duplicate]
...t only for displaying and do not need the actual data in table to change:
SELECT UPPER(LEFT(word,1))+LOWER(SUBSTRING(word,2,LEN(word))) FROM [yourtable]
Hope this helps.
EDIT: I realised about the '-' so here is my attempt to solve this problem in a function.
CREATE FUNCTION [dbo].[CapitalizeFi...
Fastest way to remove first char in a String
... random strings, that you pre-populated an array (list) with, and randomly select the element of that array (list).
– ajeh
Sep 9 '16 at 19:51
add a comment
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Concatenate multiple result rows of one column into one, group by another column [duplicate]
...Simpler with the aggregate function string_agg() (Postgres 9.0 or later):
SELECT movie, string_agg(actor, ', ') AS actor_list
FROM tbl
GROUP BY 1;
The 1 in GROUP BY 1 is a positional reference and a shortcut for GROUP BY movie in this case.
string_agg() expects data type text as input. Other ...
Why should hash functions use a prime number modulus?
...er of buckets. This is convenient and saves having to search around or pre-select a prime number of the right magnitude. So you rely on the hash function not to use even multipliers, which is generally a safe assumption. But you can still get occasional bad hashing behaviours based on hash functions...
Use '=' or LIKE to compare strings in SQL?
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To see the performance difference, try this:
SELECT count(*)
FROM master..sysobjects as A
JOIN tempdb..sysobjects as B
on A.name = B.name
SELECT count(*)
FROM master..sysobjects as A
JOIN tempdb..sysobjects as B
on A.name LIKE B.name
Comparing strings with '=' is muc...