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What is the error “Every derived table must have its own alias” in MySQL?
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@ToBe I'm curious what you meant by that? The answer holds true in any query, that if you have a derived table in your from clause you need to give it an alias.
– AdamMc331
May 4 '15 at 13:11
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What is the in a .vimrc file?
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The <Leader> key is mapped to \ by default. So if you have a map of <Leader>t, you can execute it by default with \+t. For more detail or re-assigning it using the mapleader variable, see
:help leader
To define a mapping which uses the "mapleader...
How to print the ld(linker) search path
What is the way to print the search paths that in looked by ld in the order it searches.
6 Answers
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What is the difference between JSON and Object Literal Notation?
...ne tell me what is the main difference between a JavaScript object defined by using Object Literal Notation and JSON object ?
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UIGestureRecognizer on UIImageView
...is very important to remember to enable user interaction on the image view by setting its userInteractionEnabled property to YES. UIImageView inherits from UIView, whose user interaction property is set to YES by default, however, UIImageView's user interaction property is set to NO by default.
Fro...
What is the difference between Trap and Interrupt?
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A trap is an exception in a user process. It's caused by division by zero or invalid memory access. It's also the usual way to invoke a kernel routine (a system call) because those run with a higher priority than user code. Handling is synchronous (so the user code is suspended ...
Python Regex instantly replace groups
...erences (backslash, group number) which are replaced with what was matched by the groups. Groups are counted the same as by the group(...) function, i.e. starting from 1, from left to right, by opening parentheses.
share
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Decimal number regular expression, where digit after decimal is optional
...same expression with whitespace, using the extended modifier (as supported by Perl):
/^ [+-]? ( (\d+ (\.\d*)?) | (\.\d+) ) $/x
or with comments:
/^ # Beginning of string
[+-]? # Optional plus or minus character
( # Followed by either:
( # Start of fi...
MySQL - Rows to Columns
...olumns.
Step 3: group and aggregate the extended table. We need to group by hostid, since it provides the y-values:
create view history_itemvalue_pivot as (
select
hostid,
sum(A) as A,
sum(B) as B,
sum(C) as C
from history_extended
group by hostid
);
select * from history_i...
How does the String class override the + operator?
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5.1.11. String Conversion
Any type may be converted to type String by string conversion.
A value x of primitive type T is first converted to a reference value
as if by giving it as an argument to an appropriate class instance
creation expression (§15.9):
If T is boolean, th...