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Difference between CTE and SubQuery?
...
CTE's are most useful for recursion:
WITH hier(cnt) AS (
SELECT 1
UNION ALL
SELECT cnt + 1
FROM hier
WHERE cnt < @n
)
SELECT cnt
FROM hier
will return @n rows (up to 101). Useful for calendars, dummy rowsets etc.
They are als...
Why and not taking font-family and font-size from body?
...es if you want to change their font/text styles - should be easy enough by selecting them though, as you've just done.
As far as I know, only form elements are affected. Off the top of my head: input, button, textarea, select.
...
关于php的socket初探 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...连接的模型都应该被称为多路复用，目前比较常用的有 select/poll/epoll/kqueue 这些 IO 模型（目前也有像 Apache 这种每个连接用单独的进程/线程来处理的 IO 模型，但是效率相对比较差，也很容易出问题，所以暂时不做介绍了）。在...
Remove columns from dataframe where ALL values are NA
...
dplyr now has a select_if verb that may be helpful here:
library(dplyr)
temp <- data.frame(x = 1:5, y = c(1,2,NA,4, 5), z = rep(NA, 5))
not_all_na <- function(x) any(!is.na(x))
not_any_na <- function(x) all(!is.na(x))
> temp
...
How to log PostgreSQL queries?
...ement = 'all'
#logging_collector = off to logging_collector = on
Optional: SELECT set_config('log_statement', 'all', true);
sudo /etc/init.d/postgresql restart or sudo service postgresql restart
Fire query in postgresql select 2+2
Find current log in /var/lib/pgsql/9.2/data/pg_log/
The log files t...
If table exists drop table then create it, if it does not exist just create it
...up the old table,
obviously.
Wrapping all statements with something like SELECT GET_LOCK('__upgrade', -1); ... DO RELEASE_LOCK('__upgrade'); allows to just invoke all statements sequentially without error checking, but I don't think it's a good idea: complexity increases and locking functions in M...
jQuery: Check if div with certain class name exists
...presumably because it changes the native features jQuery can use to do the selection. Here's a test case where the div exists, and here's one where it doesn't exist.
– T.J. Crowder
Apr 26 '11 at 6:10
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How to verify an XPath expression in Chrome Developers tool or Firefox's Firebug?
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In "Elements" panel, press Ctrl+F
In the search box, type in XPath or CSS Selector, if elements are found, they will be highlighted in yellow.
Firefox (since version 75)
Since FF 75 it's possible to use raw xpath query without evaluation xpath expressions, see documentation for more info.
Fir...
Java project in Eclipse: The type java.lang.Object cannot be resolved. It is indirectly referenced f
...teps could help:
Right-click on project » Properties » Java Build Path
Select Libraries tab
Find the JRE System Library and remove it
Click Add Library... button at right side » Add the JRE System Library (Workspace default JRE)
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Is there a performance difference between CTE , Sub-Query, Temporary Table or Table Variable?
...ur question. If you click on the link you will see the reasons those users selected.
– Aaron Bertrand
Jun 23 '12 at 17:13
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